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	$187.90	4.474%	$196.3066	$196.31	$196.30	$196.30
Purchase #2	$89.57	8.496%	$97.1799	$97.18	$97.20	$97.20
Purchase #3	$61.60	6.164%	$65.397	$65.40	$65.40	$65.40
Purchase #4	$67.36	7.266%	$72.2544	$72.25	$72.25	$72.30
Purchase #5	$27.87	10.778%	$30.8738	$30.87	$30.85	$30.90
Purchase #6	$83.28	7.364%	$89.4127	$89.41	$89.40	$89.40
Purchase #7	$40.32	6.734%	$43.0351	$43.04	$43.05	$43.00
7 purchase totals =	$557.90		$594.4595	$594.46	$594.45	$594.50