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	$39.85	6.840%	$42.5757	$42.58	$42.60	$42.60
Purchase #2	$38.62	12.306%	$43.3726	$43.37	$43.35	$43.40
Purchase #3	$232.90	3.851%	$241.869	$241.87	$241.85	$241.90
Purchase #4	$235.46	6.273%	$250.2304	$250.23	$250.25	$250.20
Purchase #5	$169.55	3.496%	$175.4775	$175.48	$175.50	$175.50
Purchase #6	$171.74	11.590%	$191.6447	$191.64	$191.65	$191.60
Purchase #7	$74.73	6.255%	$79.4044	$79.40	$79.40	$79.40
7 purchase totals =	$962.85		$1,024.5743	$1,024.57	$1,024.60	$1,024.60