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	$167.76	5.670%	$177.272	$177.27	$177.25	$177.30
Purchase #2	$180.34	4.308%	$188.109	$188.11	$188.10	$188.10
Purchase #3	$19.77	6.482%	$21.0515	$21.05	$21.05	$21.10
Purchase #4	$180.43	11.339%	$200.889	$200.89	$200.90	$200.90
Purchase #5	$216.67	6.227%	$230.162	$230.16	$230.15	$230.20
Purchase #6	$34.81	13.550%	$39.5268	$39.53	$39.55	$39.50
Purchase #7	$186.73	7.347%	$200.4491	$200.45	$200.45	$200.40
7 purchase totals =	$986.51		$1,057.4594	$1,057.46	$1,057.45	$1,057.50