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	$154.89	13.279%	$175.4578	$175.46	$175.45	$175.50
Purchase #2	$74.68	10.620%	$82.611	$82.61	$82.60	$82.60
Purchase #3	$147.50	12.478%	$165.9051	$165.91	$165.90	$165.90
Purchase #4	$159.35	10.641%	$176.3064	$176.31	$176.30	$176.30
Purchase #5	$35.89	6.407%	$38.1895	$38.19	$38.20	$38.20
Purchase #6	$244.72	9.195%	$267.222	$267.22	$267.20	$267.20
Purchase #7	$38.70	4.202%	$40.3262	$40.33	$40.35	$40.30
7 purchase totals =	$855.73		$946.0180	$946.03	$946.00	$946.00