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	$127.93	10.400%	$141.2347	$141.23	$141.25	$141.20
Purchase #2	$20.73	5.707%	$21.9131	$21.91	$21.90	$21.90
Purchase #3	$214.57	12.502%	$241.3955	$241.40	$241.40	$241.40
Purchase #4	$217.28	4.831%	$227.7768	$227.78	$227.80	$227.80
Purchase #5	$152.26	3.302%	$157.2876	$157.29	$157.30	$157.30
Purchase #6	$211.30	5.799%	$223.5533	$223.55	$223.55	$223.60
Purchase #7	$120.40	5.655%	$127.2086	$127.21	$127.20	$127.20
7 purchase totals =	$1,064.47		$1,140.3696	$1,140.37	$1,140.40	$1,140.40