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	$64.62	10.864%	$71.6403	$71.64	$71.65	$71.60
Purchase #2	$160.27	4.508%	$167.495	$167.50	$167.50	$167.50
Purchase #3	$176.37	10.736%	$195.3051	$195.31	$195.30	$195.30
Purchase #4	$116.89	5.801%	$123.6708	$123.67	$123.65	$123.70
Purchase #5	$160.52	4.683%	$168.0372	$168.04	$168.05	$168.00
Purchase #6	$208.35	4.537%	$217.8028	$217.80	$217.80	$217.80
Purchase #7	$205.50	11.488%	$229.1078	$229.11	$229.10	$229.10
7 purchase totals =	$1,092.52		$1,173.0590	$1,173.07	$1,173.05	$1,173.00