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	$56.82	12.871%	$64.1333	$64.13	$64.15	$64.10
Purchase #2	$84.33	13.465%	$95.685	$95.69	$95.70	$95.70
Purchase #3	$241.48	13.335%	$273.6814	$273.68	$273.70	$273.70
Purchase #4	$176.38	13.697%	$200.5388	$200.54	$200.55	$200.50
Purchase #5	$211.33	10.253%	$232.9977	$233.00	$233.00	$233.00
Purchase #6	$21.97	11.106%	$24.41	$24.41	$24.40	$24.40
Purchase #7	$188.91	3.818%	$196.1226	$196.12	$196.10	$196.10
7 purchase totals =	$981.22		$1,087.5688	$1,087.57	$1,087.60	$1,087.50