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	$25.30	11.142%	$28.1189	$28.12	$28.10	$28.10
Purchase #2	$225.80	12.758%	$254.6076	$254.61	$254.60	$254.60
Purchase #3	$190.61	11.544%	$212.614	$212.61	$212.60	$212.60
Purchase #4	$150.44	11.791%	$168.1784	$168.18	$168.20	$168.20
Purchase #5	$221.38	3.637%	$229.4316	$229.43	$229.45	$229.40
Purchase #6	$72.92	13.587%	$82.8276	$82.83	$82.85	$82.80
Purchase #7	$191.52	11.107%	$212.7921	$212.79	$212.80	$212.80
7 purchase totals =	$1,077.97		$1,188.5702	$1,188.57	$1,188.60	$1,188.50