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	$52.61	8.232%	$56.9409	$56.94	$56.95	$56.90
Purchase #2	$179.94	9.546%	$197.1171	$197.12	$197.10	$197.10
Purchase #3	$53.79	7.613%	$57.885	$57.89	$57.90	$57.90
Purchase #4	$65.59	9.414%	$71.7646	$71.76	$71.75	$71.80
Purchase #5	$168.89	6.307%	$179.5419	$179.54	$179.55	$179.50
Purchase #6	$203.92	12.690%	$229.7974	$229.80	$229.80	$229.80
Purchase #7	$208.42	7.573%	$224.2036	$224.20	$224.20	$224.20
7 purchase totals =	$933.16		$1,017.2505	$1,017.25	$1,017.25	$1,017.20