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	$40.90	13.712%	$46.5082	$46.51	$46.50	$46.50
Purchase #2	$241.81	5.635%	$255.436	$255.44	$255.45	$255.40
Purchase #3	$59.26	12.801%	$66.8459	$66.85	$66.85	$66.80
Purchase #4	$169.88	10.644%	$187.962	$187.96	$187.95	$188.00
Purchase #5	$204.64	3.119%	$211.0227	$211.02	$211.00	$211.00
Purchase #6	$161.50	10.670%	$178.7321	$178.73	$178.75	$178.70
Purchase #7	$97.52	6.308%	$103.6716	$103.67	$103.65	$103.70
7 purchase totals =	$975.51		$1,050.1785	$1,050.18	$1,050.15	$1,050.10