Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.86	13.207%	$194.5576	$194.56	$194.55	$194.60
Purchase #2	$157.56	9.682%	$172.815	$172.82	$172.80	$172.80
Purchase #3	$145.55	13.677%	$165.4569	$165.46	$165.45	$165.50
Purchase #4	$167.68	8.187%	$181.408	$181.41	$181.40	$181.40
Purchase #5	$232.58	13.648%	$264.3225	$264.32	$264.30	$264.30
Purchase #6	$100.44	9.161%	$109.6413	$109.64	$109.65	$109.60
Purchase #7	$163.61	11.333%	$182.1519	$182.15	$182.15	$182.20
7 purchase totals =	$1,139.28		$1,270.3532	$1,270.36	$1,270.30	$1,270.40