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	$191.98	10.478%	$212.0957	$212.10	$212.10	$212.10
Purchase #2	$38.54	12.732%	$43.4469	$43.45	$43.45	$43.40
Purchase #3	$77.62	7.335%	$83.3134	$83.31	$83.30	$83.30
Purchase #4	$59.56	5.348%	$62.7453	$62.75	$62.75	$62.70
Purchase #5	$141.46	13.211%	$160.1483	$160.15	$160.15	$160.10
Purchase #6	$43.54	9.204%	$47.5474	$47.55	$47.55	$47.50
Purchase #7	$210.76	5.818%	$223.022	$223.02	$223.00	$223.00
7 purchase totals =	$763.46		$832.3190	$832.33	$832.30	$832.10