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	$146.89	7.471%	$157.8642	$157.86	$157.85	$157.90
Purchase #2	$144.75	3.843%	$150.3127	$150.31	$150.30	$150.30
Purchase #3	$158.61	5.533%	$167.3859	$167.39	$167.40	$167.40
Purchase #4	$56.80	7.344%	$60.9714	$60.97	$60.95	$61.00
Purchase #5	$49.97	5.687%	$52.8118	$52.81	$52.80	$52.80
Purchase #6	$245.53	7.841%	$264.782	$264.78	$264.80	$264.80
Purchase #7	$37.74	6.720%	$40.2761	$40.28	$40.30	$40.30
7 purchase totals =	$840.29		$894.4041	$894.40	$894.40	$894.50