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	$52.25	13.420%	$59.262	$59.26	$59.25	$59.30
Purchase #2	$30.27	3.252%	$31.2544	$31.25	$31.25	$31.30
Purchase #3	$98.74	4.681%	$103.362	$103.36	$103.35	$103.40
Purchase #4	$220.99	10.757%	$244.7619	$244.76	$244.75	$244.80
Purchase #5	$199.82	10.702%	$221.2047	$221.20	$221.20	$221.20
Purchase #6	$111.70	13.714%	$127.0185	$127.02	$127.00	$127.00
Purchase #7	$58.59	4.429%	$61.185	$61.19	$61.20	$61.20
7 purchase totals =	$772.36		$848.0485	$848.04	$848.00	$848.20