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	$61.75	6.566%	$65.8045	$65.80	$65.80	$65.80
Purchase #2	$229.72	9.478%	$251.4929	$251.49	$251.50	$251.50
Purchase #3	$188.78	5.179%	$198.5569	$198.56	$198.55	$198.60
Purchase #4	$36.48	11.468%	$40.6635	$40.66	$40.65	$40.70
Purchase #5	$229.58	5.364%	$241.8947	$241.89	$241.90	$241.90
Purchase #6	$81.82	10.676%	$90.5551	$90.56	$90.55	$90.60
Purchase #7	$231.67	9.518%	$253.7204	$253.72	$253.70	$253.70
7 purchase totals =	$1,059.80		$1,142.6880	$1,142.68	$1,142.65	$1,142.80