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	$152.98	13.526%	$173.6721	$173.67	$173.65	$173.70
Purchase #2	$142.48	5.237%	$149.9417	$149.94	$149.95	$149.90
Purchase #3	$245.83	13.501%	$279.0195	$279.02	$279.00	$279.00
Purchase #4	$57.83	8.730%	$62.8786	$62.88	$62.90	$62.90
Purchase #5	$28.90	11.873%	$32.3313	$32.33	$32.35	$32.30
Purchase #6	$172.31	7.653%	$185.4969	$185.50	$185.50	$185.50
Purchase #7	$154.49	6.303%	$164.2275	$164.23	$164.25	$164.20
7 purchase totals =	$954.82		$1,047.5676	$1,047.57	$1,047.60	$1,047.50