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	$105.44	5.646%	$111.3931	$111.39	$111.40	$111.40
Purchase #2	$234.91	12.282%	$263.7616	$263.76	$263.75	$263.80
Purchase #3	$81.57	12.215%	$91.5338	$91.53	$91.55	$91.50
Purchase #4	$239.48	6.243%	$254.4307	$254.43	$254.45	$254.40
Purchase #5	$222.79	13.703%	$253.3189	$253.32	$253.30	$253.30
Purchase #6	$90.78	10.512%	$100.3228	$100.32	$100.30	$100.30
Purchase #7	$46.89	12.530%	$52.7653	$52.77	$52.75	$52.80
7 purchase totals =	$1,021.86		$1,127.5262	$1,127.52	$1,127.50	$1,127.50