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	$82.70	3.179%	$85.329	$85.33	$85.35	$85.30
Purchase #2	$171.40	6.268%	$182.1434	$182.14	$182.15	$182.10
Purchase #3	$227.65	11.614%	$254.0893	$254.09	$254.10	$254.10
Purchase #4	$71.44	11.580%	$79.7128	$79.71	$79.70	$79.70
Purchase #5	$102.39	7.865%	$110.443	$110.44	$110.45	$110.40
Purchase #6	$141.47	4.691%	$148.1064	$148.11	$148.10	$148.10
Purchase #7	$142.72	6.703%	$152.2865	$152.29	$152.30	$152.30
7 purchase totals =	$939.77		$1,012.1104	$1,012.11	$1,012.15	$1,012.00