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	$198.83	7.705%	$214.1499	$214.15	$214.15	$214.10
Purchase #2	$89.48	9.762%	$98.215	$98.22	$98.20	$98.20
Purchase #3	$64.97	9.506%	$71.146	$71.15	$71.15	$71.10
Purchase #4	$59.79	12.722%	$67.3965	$67.40	$67.40	$67.40
Purchase #5	$19.85	9.805%	$21.7963	$21.80	$21.80	$21.80
Purchase #6	$113.63	13.872%	$129.3928	$129.39	$129.40	$129.40
Purchase #7	$87.25	13.219%	$98.7836	$98.78	$98.80	$98.80
7 purchase totals =	$633.80		$700.8801	$700.89	$700.90	$700.80