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	$247.66	7.169%	$265.4147	$265.41	$265.40	$265.40
Purchase #2	$204.77	6.590%	$218.2643	$218.26	$218.25	$218.30
Purchase #3	$194.62	10.622%	$215.2925	$215.29	$215.30	$215.30
Purchase #4	$150.54	9.467%	$164.7916	$164.79	$164.80	$164.80
Purchase #5	$65.40	3.563%	$67.7302	$67.73	$67.75	$67.70
Purchase #6	$116.45	9.152%	$127.1075	$127.11	$127.10	$127.10
Purchase #7	$47.89	5.796%	$50.6657	$50.67	$50.65	$50.70
7 purchase totals =	$1,027.33		$1,109.2665	$1,109.26	$1,109.25	$1,109.30