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	$156.77	7.549%	$168.6046	$168.60	$168.60	$168.60
Purchase #2	$71.54	11.122%	$79.4967	$79.50	$79.50	$79.50
Purchase #3	$149.97	6.322%	$159.4511	$159.45	$159.45	$159.50
Purchase #4	$175.77	5.527%	$185.4848	$185.48	$185.50	$185.50
Purchase #5	$104.66	6.314%	$111.2682	$111.27	$111.25	$111.30
Purchase #6	$105.29	8.778%	$114.5324	$114.53	$114.55	$114.50
Purchase #7	$246.62	7.760%	$265.7577	$265.76	$265.75	$265.80
7 purchase totals =	$1,010.62		$1,084.5955	$1,084.59	$1,084.60	$1,084.70