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	$190.96	9.343%	$208.8014	$208.80	$208.80	$208.80
Purchase #2	$81.92	11.634%	$91.4506	$91.45	$91.45	$91.50
Purchase #3	$82.26	9.218%	$89.8427	$89.84	$89.85	$89.80
Purchase #4	$141.30	12.183%	$158.5146	$158.51	$158.50	$158.50
Purchase #5	$235.97	9.772%	$259.029	$259.03	$259.05	$259.00
Purchase #6	$83.78	8.753%	$91.1133	$91.11	$91.10	$91.10
Purchase #7	$130.48	9.551%	$142.9421	$142.94	$142.95	$142.90
7 purchase totals =	$946.67		$1,041.6937	$1,041.68	$1,041.70	$1,041.60