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	$171.68	7.675%	$184.8564	$184.86	$184.85	$184.90
Purchase #2	$154.64	7.680%	$166.5164	$166.52	$166.50	$166.50
Purchase #3	$114.45	5.758%	$121.04	$121.04	$121.05	$121.00
Purchase #4	$154.34	10.870%	$171.1168	$171.12	$171.10	$171.10
Purchase #5	$40.36	3.527%	$41.7835	$41.78	$41.80	$41.80
Purchase #6	$220.65	11.148%	$245.2481	$245.25	$245.25	$245.20
Purchase #7	$131.98	13.773%	$150.1576	$150.16	$150.15	$150.20
7 purchase totals =	$988.10		$1,080.7188	$1,080.73	$1,080.70	$1,080.70