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	$103.29	7.516%	$111.0533	$111.05	$111.05	$111.10
Purchase #2	$88.42	7.770%	$95.2902	$95.29	$95.30	$95.30
Purchase #3	$223.49	6.741%	$238.5555	$238.56	$238.55	$238.60
Purchase #4	$77.34	12.404%	$86.9333	$86.93	$86.95	$86.90
Purchase #5	$53.35	12.581%	$60.062	$60.06	$60.05	$60.10
Purchase #6	$128.90	8.586%	$139.9674	$139.97	$139.95	$140.00
Purchase #7	$29.28	8.107%	$31.6537	$31.65	$31.65	$31.70
7 purchase totals =	$704.07		$763.5154	$763.51	$763.50	$763.70