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	$185.53	13.341%	$210.2816	$210.28	$210.30	$210.30
Purchase #2	$108.56	13.734%	$123.4696	$123.47	$123.45	$123.50
Purchase #3	$53.58	12.800%	$60.4382	$60.44	$60.45	$60.40
Purchase #4	$176.70	7.250%	$189.5108	$189.51	$189.50	$189.50
Purchase #5	$111.54	9.793%	$122.4631	$122.46	$122.45	$122.50
Purchase #6	$97.98	3.692%	$101.5974	$101.60	$101.60	$101.60
Purchase #7	$231.84	10.689%	$256.6214	$256.62	$256.60	$256.60
7 purchase totals =	$965.73		$1,064.3821	$1,064.38	$1,064.35	$1,064.40