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	$56.35	3.406%	$58.2693	$58.27	$58.25	$58.30
Purchase #2	$67.48	3.302%	$69.7082	$69.71	$69.70	$69.70
Purchase #3	$131.37	11.717%	$146.7626	$146.76	$146.75	$146.80
Purchase #4	$181.32	4.715%	$189.8692	$189.87	$189.85	$189.90
Purchase #5	$68.47	5.555%	$72.2735	$72.27	$72.25	$72.30
Purchase #6	$213.41	9.426%	$233.526	$233.53	$233.55	$233.50
Purchase #7	$99.71	4.231%	$103.9287	$103.93	$103.95	$103.90
7 purchase totals =	$818.11		$874.3375	$874.34	$874.30	$874.40