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	$48.71	3.357%	$50.3452	$50.35	$50.35	$50.30
Purchase #2	$97.42	4.121%	$101.4347	$101.43	$101.45	$101.40
Purchase #3	$201.30	6.250%	$213.8813	$213.88	$213.90	$213.90
Purchase #4	$240.87	9.363%	$263.4227	$263.42	$263.40	$263.40
Purchase #5	$182.38	4.820%	$191.1707	$191.17	$191.15	$191.20
Purchase #6	$102.39	13.433%	$116.144	$116.14	$116.15	$116.10
Purchase #7	$29.67	10.807%	$32.8764	$32.88	$32.90	$32.90
7 purchase totals =	$902.74		$969.2750	$969.27	$969.30	$969.20