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	$142.25	11.290%	$158.31	$158.31	$158.30	$158.30
Purchase #2	$176.27	6.861%	$188.3639	$188.36	$188.35	$188.40
Purchase #3	$106.66	8.590%	$115.8221	$115.82	$115.80	$115.80
Purchase #4	$141.47	5.173%	$148.7882	$148.79	$148.80	$148.80
Purchase #5	$158.55	4.221%	$165.2424	$165.24	$165.25	$165.20
Purchase #6	$37.80	12.456%	$42.5084	$42.51	$42.50	$42.50
Purchase #7	$210.89	9.814%	$231.5867	$231.59	$231.60	$231.60
7 purchase totals =	$973.89		$1,050.6217	$1,050.62	$1,050.60	$1,050.60