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	$222.71	8.718%	$242.1259	$242.13	$242.15	$242.10
Purchase #2	$222.50	8.170%	$240.6783	$240.68	$240.70	$240.70
Purchase #3	$191.29	5.721%	$202.2337	$202.23	$202.25	$202.20
Purchase #4	$38.40	6.608%	$40.9375	$40.94	$40.95	$40.90
Purchase #5	$88.89	10.397%	$98.1319	$98.13	$98.15	$98.10
Purchase #6	$100.62	4.375%	$105.0221	$105.02	$105.00	$105.00
Purchase #7	$135.31	3.422%	$139.9403	$139.94	$139.95	$139.90
7 purchase totals =	$999.72		$1,069.0697	$1,069.07	$1,069.15	$1,068.90