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	$32.31	3.815%	$33.5426	$33.54	$33.55	$33.50
Purchase #2	$105.25	10.504%	$116.3055	$116.31	$116.30	$116.30
Purchase #3	$157.55	11.363%	$175.4524	$175.45	$175.45	$175.50
Purchase #4	$49.55	11.748%	$55.3711	$55.37	$55.35	$55.40
Purchase #5	$193.64	6.355%	$205.9458	$205.95	$205.95	$205.90
Purchase #6	$89.98	13.269%	$101.9194	$101.92	$101.90	$101.90
Purchase #7	$93.26	6.507%	$99.3284	$99.33	$99.35	$99.30
7 purchase totals =	$721.54		$787.8652	$787.87	$787.85	$787.80