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	$92.41	13.644%	$105.0184	$105.02	$105.00	$105.00
Purchase #2	$52.58	6.304%	$55.8946	$55.89	$55.90	$55.90
Purchase #3	$205.89	12.194%	$230.9962	$231.00	$231.00	$231.00
Purchase #4	$196.58	10.322%	$216.871	$216.87	$216.85	$216.90
Purchase #5	$229.73	11.627%	$256.4407	$256.44	$256.45	$256.40
Purchase #6	$33.96	9.632%	$37.231	$37.23	$37.25	$37.20
Purchase #7	$113.42	6.336%	$120.6063	$120.61	$120.60	$120.60
7 purchase totals =	$924.57		$1,023.0582	$1,023.06	$1,023.05	$1,023.00