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	$167.99	13.785%	$191.1474	$191.15	$191.15	$191.10
Purchase #2	$147.42	11.747%	$164.7374	$164.74	$164.75	$164.70
Purchase #3	$160.59	3.751%	$166.6137	$166.61	$166.60	$166.60
Purchase #4	$181.88	12.482%	$204.5823	$204.58	$204.60	$204.60
Purchase #5	$165.98	3.607%	$171.9669	$171.97	$171.95	$172.00
Purchase #6	$181.39	8.343%	$196.5234	$196.52	$196.50	$196.50
Purchase #7	$83.38	7.398%	$89.5485	$89.55	$89.55	$89.50
7 purchase totals =	$1,088.63		$1,185.1196	$1,185.12	$1,185.10	$1,185.00