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	$228.51	11.187%	$254.0734	$254.07	$254.05	$254.10
Purchase #2	$130.58	11.114%	$145.0927	$145.09	$145.10	$145.10
Purchase #3	$82.45	12.428%	$92.6969	$92.70	$92.70	$92.70
Purchase #4	$19.81	8.594%	$21.5125	$21.51	$21.50	$21.50
Purchase #5	$209.56	9.788%	$230.0717	$230.07	$230.05	$230.10
Purchase #6	$93.88	6.815%	$100.2779	$100.28	$100.30	$100.30
Purchase #7	$147.82	12.151%	$165.7816	$165.78	$165.80	$165.80
7 purchase totals =	$912.61		$1,009.5067	$1,009.50	$1,009.50	$1,009.60