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	$150.59	13.500%	$170.9197	$170.92	$170.90	$170.90
Purchase #2	$223.36	4.344%	$233.0628	$233.06	$233.05	$233.10
Purchase #3	$105.46	8.189%	$114.0961	$114.10	$114.10	$114.10
Purchase #4	$48.31	4.349%	$50.411	$50.41	$50.40	$50.40
Purchase #5	$175.81	11.801%	$196.5573	$196.56	$196.55	$196.60
Purchase #6	$18.78	8.198%	$20.3196	$20.32	$20.30	$20.30
Purchase #7	$232.57	6.261%	$247.1312	$247.13	$247.15	$247.10
7 purchase totals =	$954.88		$1,032.4977	$1,032.50	$1,032.45	$1,032.50