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	$228.61	3.134%	$235.7746	$235.77	$235.75	$235.80
Purchase #2	$28.50	11.505%	$31.7789	$31.78	$31.80	$31.80
Purchase #3	$196.96	13.573%	$223.6934	$223.69	$223.70	$223.70
Purchase #4	$115.87	12.512%	$130.3677	$130.37	$130.35	$130.40
Purchase #5	$223.74	7.496%	$240.5116	$240.51	$240.50	$240.50
Purchase #6	$17.42	7.747%	$18.7695	$18.77	$18.75	$18.80
Purchase #7	$210.40	6.429%	$223.9266	$223.93	$223.95	$223.90
7 purchase totals =	$1,021.50		$1,104.8223	$1,104.82	$1,104.80	$1,104.90