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	$67.91	4.374%	$70.8804	$70.88	$70.90	$70.90
Purchase #2	$101.88	12.499%	$114.614	$114.61	$114.60	$114.60
Purchase #3	$20.49	4.786%	$21.4707	$21.47	$21.45	$21.50
Purchase #4	$232.69	4.635%	$243.4752	$243.48	$243.50	$243.50
Purchase #5	$165.55	11.394%	$184.4128	$184.41	$184.40	$184.40
Purchase #6	$190.96	13.414%	$216.5754	$216.58	$216.60	$216.60
Purchase #7	$193.68	8.325%	$209.8039	$209.80	$209.80	$209.80
7 purchase totals =	$973.16		$1,061.2324	$1,061.23	$1,061.25	$1,061.30