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	$213.54	10.396%	$235.7396	$235.74	$235.75	$235.70
Purchase #2	$240.78	10.191%	$265.3179	$265.32	$265.30	$265.30
Purchase #3	$145.91	4.606%	$152.6306	$152.63	$152.65	$152.60
Purchase #4	$133.89	8.760%	$145.6188	$145.62	$145.60	$145.60
Purchase #5	$130.75	13.369%	$148.23	$148.23	$148.25	$148.20
Purchase #6	$109.56	6.287%	$116.448	$116.45	$116.45	$116.40
Purchase #7	$237.85	11.800%	$265.9163	$265.92	$265.90	$265.90
7 purchase totals =	$1,212.28		$1,329.9012	$1,329.91	$1,329.90	$1,329.70