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	$147.98	3.152%	$152.6443	$152.64	$152.65	$152.60
Purchase #2	$182.32	4.496%	$190.5171	$190.52	$190.50	$190.50
Purchase #3	$127.41	5.214%	$134.0532	$134.05	$134.05	$134.10
Purchase #4	$174.49	11.787%	$195.0571	$195.06	$195.05	$195.10
Purchase #5	$168.59	9.565%	$184.7156	$184.72	$184.70	$184.70
Purchase #6	$104.64	13.871%	$119.1546	$119.15	$119.15	$119.20
Purchase #7	$158.67	8.723%	$172.5108	$172.51	$172.50	$172.50
7 purchase totals =	$1,064.10		$1,148.6527	$1,148.65	$1,148.60	$1,148.70