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	$157.84	9.155%	$172.2903	$172.29	$172.30	$172.30
Purchase #2	$231.63	11.802%	$258.967	$258.97	$258.95	$259.00
Purchase #3	$26.40	9.747%	$28.9732	$28.97	$28.95	$29.00
Purchase #4	$100.72	9.118%	$109.9036	$109.90	$109.90	$109.90
Purchase #5	$128.80	5.840%	$136.3219	$136.32	$136.30	$136.30
Purchase #6	$154.44	6.451%	$164.4029	$164.40	$164.40	$164.40
Purchase #7	$249.32	10.494%	$275.4836	$275.48	$275.50	$275.50
7 purchase totals =	$1,049.15		$1,146.3425	$1,146.33	$1,146.30	$1,146.40