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	9.848%	$70.9838	$70.98	$71.00	$71.00
Purchase #2	$166.55	3.620%	$172.5791	$172.58	$172.60	$172.60
Purchase #3	$152.49	7.817%	$164.4101	$164.41	$164.40	$164.40
Purchase #4	$173.30	6.565%	$184.6771	$184.68	$184.70	$184.70
Purchase #5	$248.54	6.290%	$264.1732	$264.17	$264.15	$264.20
Purchase #6	$164.50	13.697%	$187.0316	$187.03	$187.05	$187.00
Purchase #7	$37.84	7.367%	$40.6277	$40.63	$40.65	$40.60
7 purchase totals =	$1,007.84		$1,084.4826	$1,084.48	$1,084.55	$1,084.50