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	$52.89	4.860%	$55.4605	$55.46	$55.45	$55.50
Purchase #2	$189.59	11.510%	$211.4118	$211.41	$211.40	$211.40
Purchase #3	$60.69	11.416%	$67.6184	$67.62	$67.60	$67.60
Purchase #4	$95.59	3.700%	$99.1268	$99.13	$99.15	$99.10
Purchase #5	$58.90	5.793%	$62.3121	$62.31	$62.30	$62.30
Purchase #6	$139.93	7.485%	$150.4038	$150.40	$150.40	$150.40
Purchase #7	$76.71	7.728%	$82.6381	$82.64	$82.65	$82.60
7 purchase totals =	$674.30		$728.9715	$728.97	$728.95	$728.90