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	$98.36	6.626%	$104.8773	$104.88	$104.90	$104.90
Purchase #2	$77.61	10.515%	$85.7707	$85.77	$85.75	$85.80
Purchase #3	$69.99	4.197%	$72.9275	$72.93	$72.95	$72.90
Purchase #4	$71.89	12.779%	$81.0768	$81.08	$81.10	$81.10
Purchase #5	$54.84	8.549%	$59.5283	$59.53	$59.55	$59.50
Purchase #6	$212.80	11.496%	$237.2635	$237.26	$237.25	$237.30
Purchase #7	$100.82	8.785%	$109.677	$109.68	$109.70	$109.70
7 purchase totals =	$686.31		$751.1211	$751.13	$751.20	$751.20