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	$93.76	13.425%	$106.3473	$106.35	$106.35	$106.30
Purchase #2	$249.65	12.772%	$281.5353	$281.54	$281.55	$281.50
Purchase #3	$55.89	8.841%	$60.8312	$60.83	$60.85	$60.80
Purchase #4	$54.87	7.397%	$58.9287	$58.93	$58.95	$58.90
Purchase #5	$58.81	5.139%	$61.8322	$61.83	$61.85	$61.80
Purchase #6	$65.41	3.531%	$67.7196	$67.72	$67.70	$67.70
Purchase #7	$98.38	13.114%	$111.2816	$111.28	$111.30	$111.30
7 purchase totals =	$676.77		$748.4759	$748.48	$748.55	$748.30