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	$111.97	11.708%	$125.0794	$125.08	$125.10	$125.10
Purchase #2	$69.40	13.232%	$78.583	$78.58	$78.60	$78.60
Purchase #3	$240.25	7.765%	$258.9054	$258.91	$258.90	$258.90
Purchase #4	$229.49	7.507%	$246.7178	$246.72	$246.70	$246.70
Purchase #5	$133.51	10.806%	$147.9371	$147.94	$147.95	$147.90
Purchase #6	$114.77	7.364%	$123.2217	$123.22	$123.20	$123.20
Purchase #7	$184.89	8.351%	$200.3302	$200.33	$200.35	$200.30
7 purchase totals =	$1,084.28		$1,180.7746	$1,180.78	$1,180.80	$1,180.70