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	$47.55	10.135%	$52.3692	$52.37	$52.35	$52.40
Purchase #2	$108.35	3.814%	$112.4825	$112.48	$112.50	$112.50
Purchase #3	$138.91	13.665%	$157.8921	$157.89	$157.90	$157.90
Purchase #4	$159.27	9.336%	$174.1394	$174.14	$174.15	$174.10
Purchase #5	$105.31	5.531%	$111.1347	$111.13	$111.15	$111.10
Purchase #6	$188.37	13.317%	$213.4552	$213.46	$213.45	$213.50
Purchase #7	$45.52	4.790%	$47.7004	$47.70	$47.70	$47.70
7 purchase totals =	$793.28		$869.1735	$869.17	$869.20	$869.20