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	$88.39	7.755%	$95.2446	$95.24	$95.25	$95.20
Purchase #2	$183.34	4.110%	$190.8753	$190.88	$190.90	$190.90
Purchase #3	$150.30	3.699%	$155.8596	$155.86	$155.85	$155.90
Purchase #4	$75.61	6.813%	$80.7613	$80.76	$80.75	$80.80
Purchase #5	$165.91	13.652%	$188.56	$188.56	$188.55	$188.60
Purchase #6	$124.46	9.824%	$136.687	$136.69	$136.70	$136.70
Purchase #7	$91.83	9.571%	$100.619	$100.62	$100.60	$100.60
7 purchase totals =	$879.84		$948.6068	$948.61	$948.60	$948.70