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	$154.95	7.446%	$166.4876	$166.49	$166.50	$166.50
Purchase #2	$89.38	6.262%	$94.977	$94.98	$95.00	$95.00
Purchase #3	$139.88	4.703%	$146.4586	$146.46	$146.45	$146.50
Purchase #4	$156.88	6.797%	$167.5431	$167.54	$167.55	$167.50
Purchase #5	$68.85	13.359%	$78.0477	$78.05	$78.05	$78.00
Purchase #6	$34.55	11.221%	$38.4269	$38.43	$38.45	$38.40
Purchase #7	$126.70	4.471%	$132.3648	$132.36	$132.35	$132.40
7 purchase totals =	$771.19		$824.3057	$824.31	$824.35	$824.30