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	$161.46	11.326%	$179.747	$179.75	$179.75	$179.70
Purchase #2	$179.50	5.475%	$189.3276	$189.33	$189.35	$189.30
Purchase #3	$176.56	10.311%	$194.7651	$194.77	$194.75	$194.80
Purchase #4	$180.89	10.335%	$199.585	$199.59	$199.60	$199.60
Purchase #5	$28.98	10.569%	$32.0429	$32.04	$32.05	$32.00
Purchase #6	$160.98	6.503%	$171.4485	$171.45	$171.45	$171.40
Purchase #7	$235.94	10.400%	$260.4778	$260.48	$260.50	$260.50
7 purchase totals =	$1,124.31		$1,227.3939	$1,227.41	$1,227.45	$1,227.30