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	$151.65	10.518%	$167.6005	$167.60	$167.60	$167.60
Purchase #2	$246.67	7.796%	$265.9004	$265.90	$265.90	$265.90
Purchase #3	$180.35	11.389%	$200.8901	$200.89	$200.90	$200.90
Purchase #4	$58.82	9.254%	$64.2632	$64.26	$64.25	$64.30
Purchase #5	$151.47	13.173%	$171.4231	$171.42	$171.40	$171.40
Purchase #6	$245.75	10.751%	$272.1706	$272.17	$272.15	$272.20
Purchase #7	$212.98	10.584%	$235.5218	$235.52	$235.50	$235.50
7 purchase totals =	$1,247.69		$1,377.7697	$1,377.76	$1,377.70	$1,377.80