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	$168.61	12.862%	$190.2966	$190.30	$190.30	$190.30
Purchase #2	$78.71	5.390%	$82.9525	$82.95	$82.95	$83.00
Purchase #3	$161.47	8.469%	$175.1449	$175.14	$175.15	$175.10
Purchase #4	$180.97	4.156%	$188.4911	$188.49	$188.50	$188.50
Purchase #5	$72.57	5.314%	$76.4264	$76.43	$76.45	$76.40
Purchase #6	$182.28	4.477%	$190.4407	$190.44	$190.45	$190.40
Purchase #7	$26.25	5.404%	$27.6686	$27.67	$27.65	$27.70
7 purchase totals =	$870.86		$931.4208	$931.42	$931.45	$931.40