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	$154.88	12.590%	$174.3794	$174.38	$174.40	$174.40
Purchase #2	$37.65	12.300%	$42.281	$42.28	$42.30	$42.30
Purchase #3	$210.54	13.854%	$239.7082	$239.71	$239.70	$239.70
Purchase #4	$18.57	6.505%	$19.778	$19.78	$19.80	$19.80
Purchase #5	$208.40	3.830%	$216.3817	$216.38	$216.40	$216.40
Purchase #6	$129.75	11.323%	$144.4416	$144.44	$144.45	$144.40
Purchase #7	$111.61	6.127%	$118.4483	$118.45	$118.45	$118.40
7 purchase totals =	$871.40		$955.4182	$955.42	$955.50	$955.40