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	$47.83	11.360%	$53.2635	$53.26	$53.25	$53.30
Purchase #2	$141.76	8.865%	$154.327	$154.33	$154.35	$154.30
Purchase #3	$133.72	12.836%	$150.8843	$150.88	$150.90	$150.90
Purchase #4	$173.34	6.118%	$183.9449	$183.94	$183.95	$183.90
Purchase #5	$195.78	13.433%	$222.0791	$222.08	$222.10	$222.10
Purchase #6	$88.43	13.544%	$100.407	$100.41	$100.40	$100.40
Purchase #7	$247.50	9.595%	$271.2476	$271.25	$271.25	$271.20
7 purchase totals =	$1,028.36		$1,136.1534	$1,136.15	$1,136.20	$1,136.10