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	$154.65	13.264%	$175.1628	$175.16	$175.15	$175.20
Purchase #2	$231.89	6.755%	$247.5542	$247.55	$247.55	$247.60
Purchase #3	$20.69	5.481%	$21.824	$21.82	$21.80	$21.80
Purchase #4	$6.88	8.423%	$7.4595	$7.46	$7.45	$7.50
Purchase #5	$98.91	12.598%	$111.3707	$111.37	$111.35	$111.40
Purchase #6	$225.75	6.343%	$240.0693	$240.07	$240.05	$240.10
Purchase #7	$228.88	3.445%	$236.7649	$236.76	$236.75	$236.80
7 purchase totals =	$967.65		$1,040.2054	$1,040.19	$1,040.10	$1,040.40