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	$123.55	5.851%	$130.7789	$130.78	$130.80	$130.80
Purchase #2	$151.41	3.377%	$156.5231	$156.52	$156.50	$156.50
Purchase #3	$53.51	3.732%	$55.507	$55.51	$55.50	$55.50
Purchase #4	$96.83	8.211%	$104.7807	$104.78	$104.80	$104.80
Purchase #5	$194.82	9.133%	$212.6129	$212.61	$212.60	$212.60
Purchase #6	$58.45	7.151%	$62.6298	$62.63	$62.65	$62.60
Purchase #7	$7.36	12.768%	$8.2997	$8.30	$8.30	$8.30
7 purchase totals =	$685.93		$731.1321	$731.13	$731.15	$731.10