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	$101.70	3.590%	$105.351	$105.35	$105.35	$105.40
Purchase #2	$39.71	6.457%	$42.2741	$42.27	$42.25	$42.30
Purchase #3	$175.81	7.858%	$189.6251	$189.63	$189.65	$189.60
Purchase #4	$196.85	12.829%	$222.1039	$222.10	$222.10	$222.10
Purchase #5	$55.36	10.218%	$61.0167	$61.02	$61.00	$61.00
Purchase #6	$115.28	4.621%	$120.6071	$120.61	$120.60	$120.60
Purchase #7	$172.81	10.797%	$191.4683	$191.47	$191.45	$191.50
7 purchase totals =	$857.52		$932.4462	$932.45	$932.40	$932.50