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	$130.36	7.485%	$140.1174	$140.12	$140.10	$140.10
Purchase #2	$135.61	4.572%	$141.8101	$141.81	$141.80	$141.80
Purchase #3	$52.53	10.642%	$58.1202	$58.12	$58.10	$58.10
Purchase #4	$139.77	8.670%	$151.8881	$151.89	$151.90	$151.90
Purchase #5	$98.77	6.840%	$105.5259	$105.53	$105.55	$105.50
Purchase #6	$221.54	10.655%	$245.1451	$245.15	$245.15	$245.10
Purchase #7	$89.76	4.574%	$93.8656	$93.87	$93.85	$93.90
7 purchase totals =	$868.34		$936.4724	$936.49	$936.45	$936.40