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	$103.99	6.231%	$110.4696	$110.47	$110.45	$110.50
Purchase #2	$212.52	4.546%	$222.1812	$222.18	$222.20	$222.20
Purchase #3	$103.93	13.196%	$117.6446	$117.64	$117.65	$117.60
Purchase #4	$95.67	4.134%	$99.625	$99.63	$99.65	$99.60
Purchase #5	$129.32	10.289%	$142.6257	$142.63	$142.65	$142.60
Purchase #6	$146.52	11.130%	$162.8277	$162.83	$162.85	$162.80
Purchase #7	$223.32	11.657%	$249.3524	$249.35	$249.35	$249.40
7 purchase totals =	$1,015.27		$1,104.7262	$1,104.73	$1,104.80	$1,104.70