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	$143.95	4.485%	$150.4062	$150.41	$150.40	$150.40
Purchase #2	$193.74	10.239%	$213.577	$213.58	$213.60	$213.60
Purchase #3	$192.35	13.392%	$218.1095	$218.11	$218.10	$218.10
Purchase #4	$59.25	11.179%	$65.8736	$65.87	$65.85	$65.90
Purchase #5	$91.83	13.173%	$103.9268	$103.93	$103.95	$103.90
Purchase #6	$229.69	12.369%	$258.1004	$258.10	$258.10	$258.10
Purchase #7	$88.79	3.187%	$91.6197	$91.62	$91.60	$91.60
7 purchase totals =	$999.60		$1,101.6132	$1,101.62	$1,101.60	$1,101.60