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	$134.31	5.282%	$141.4043	$141.40	$141.40	$141.40
Purchase #2	$97.98	5.121%	$102.9976	$103.00	$103.00	$103.00
Purchase #3	$82.71	7.822%	$89.1796	$89.18	$89.20	$89.20
Purchase #4	$57.65	3.258%	$59.5282	$59.53	$59.55	$59.50
Purchase #5	$147.44	8.215%	$159.5522	$159.55	$159.55	$159.60
Purchase #6	$167.86	6.142%	$178.17	$178.17	$178.15	$178.20
Purchase #7	$66.77	7.360%	$71.6843	$71.68	$71.70	$71.70
7 purchase totals =	$754.72		$802.5162	$802.51	$802.55	$802.60