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	$147.34	5.729%	$155.7811	$155.78	$155.80	$155.80
Purchase #2	$107.66	5.223%	$113.2831	$113.28	$113.30	$113.30
Purchase #3	$231.43	10.527%	$255.7926	$255.79	$255.80	$255.80
Purchase #4	$19.95	3.201%	$20.5886	$20.59	$20.60	$20.60
Purchase #5	$70.96	9.493%	$77.6962	$77.70	$77.70	$77.70
Purchase #6	$221.29	10.813%	$245.2181	$245.22	$245.20	$245.20
Purchase #7	$182.42	7.761%	$196.5776	$196.58	$196.60	$196.60
7 purchase totals =	$981.05		$1,064.9373	$1,064.94	$1,065.00	$1,065.00