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	$232.51	6.237%	$247.0116	$247.01	$247.00	$247.00
Purchase #2	$93.31	11.834%	$104.3523	$104.35	$104.35	$104.40
Purchase #3	$215.41	6.807%	$230.073	$230.07	$230.05	$230.10
Purchase #4	$166.75	12.764%	$188.034	$188.03	$188.05	$188.00
Purchase #5	$201.69	3.868%	$209.4914	$209.49	$209.50	$209.50
Purchase #6	$97.97	7.565%	$105.3814	$105.38	$105.40	$105.40
Purchase #7	$55.58	7.551%	$59.7768	$59.78	$59.80	$59.80
7 purchase totals =	$1,063.22		$1,144.1205	$1,144.11	$1,144.15	$1,144.20