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	$94.54	6.760%	$100.9309	$100.93	$100.95	$100.90
Purchase #2	$34.34	10.133%	$37.8197	$37.82	$37.80	$37.80
Purchase #3	$36.79	3.138%	$37.9445	$37.94	$37.95	$37.90
Purchase #4	$83.65	10.763%	$92.6532	$92.65	$92.65	$92.70
Purchase #5	$162.91	7.466%	$175.0729	$175.07	$175.05	$175.10
Purchase #6	$91.33	8.486%	$99.0803	$99.08	$99.10	$99.10
Purchase #7	$112.35	5.579%	$118.618	$118.62	$118.60	$118.60
7 purchase totals =	$615.91		$662.1195	$662.11	$662.10	$662.10