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	$65.64	10.234%	$72.3576	$72.36	$72.35	$72.40
Purchase #2	$161.85	6.132%	$171.7746	$171.77	$171.75	$171.80
Purchase #3	$178.53	7.472%	$191.8698	$191.87	$191.85	$191.90
Purchase #4	$51.25	13.368%	$58.1011	$58.10	$58.10	$58.10
Purchase #5	$24.89	12.538%	$28.0107	$28.01	$28.00	$28.00
Purchase #6	$54.35	12.417%	$61.0986	$61.10	$61.10	$61.10
Purchase #7	$95.76	10.198%	$105.5256	$105.53	$105.55	$105.50
7 purchase totals =	$632.27		$688.7380	$688.74	$688.70	$688.80