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	$126.72	3.585%	$131.2629	$131.26	$131.25	$131.30
Purchase #2	$31.49	5.728%	$33.2937	$33.29	$33.30	$33.30
Purchase #3	$127.74	7.107%	$136.8185	$136.82	$136.80	$136.80
Purchase #4	$224.45	13.189%	$254.0527	$254.05	$254.05	$254.10
Purchase #5	$128.91	13.648%	$146.5036	$146.50	$146.50	$146.50
Purchase #6	$57.37	7.742%	$61.8116	$61.81	$61.80	$61.80
Purchase #7	$104.61	5.654%	$110.5246	$110.52	$110.50	$110.50
7 purchase totals =	$801.29		$874.2676	$874.25	$874.20	$874.30