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	$104.48	13.302%	$118.3779	$118.38	$118.40	$118.40
Purchase #2	$155.42	6.487%	$165.5021	$165.50	$165.50	$165.50
Purchase #3	$79.34	3.855%	$82.3986	$82.40	$82.40	$82.40
Purchase #4	$18.56	7.130%	$19.8833	$19.88	$19.90	$19.90
Purchase #5	$95.56	8.643%	$103.8193	$103.82	$103.80	$103.80
Purchase #6	$118.99	13.465%	$135.012	$135.01	$135.00	$135.00
Purchase #7	$134.90	12.283%	$151.4698	$151.47	$151.45	$151.50
7 purchase totals =	$707.25		$776.4630	$776.46	$776.45	$776.50