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	$166.49	3.699%	$172.6485	$172.65	$172.65	$172.60
Purchase #2	$48.41	3.445%	$50.0777	$50.08	$50.10	$50.10
Purchase #3	$65.73	10.589%	$72.6901	$72.69	$72.70	$72.70
Purchase #4	$172.85	10.409%	$190.842	$190.84	$190.85	$190.80
Purchase #5	$51.49	6.570%	$54.8729	$54.87	$54.85	$54.90
Purchase #6	$169.46	7.386%	$181.9763	$181.98	$182.00	$182.00
Purchase #7	$32.74	5.322%	$34.4824	$34.48	$34.50	$34.50
7 purchase totals =	$707.17		$757.5899	$757.59	$757.65	$757.60