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	$107.46	3.507%	$111.2286	$111.23	$111.25	$111.20
Purchase #2	$234.87	6.775%	$250.7824	$250.78	$250.80	$250.80
Purchase #3	$47.87	11.340%	$53.2985	$53.30	$53.30	$53.30
Purchase #4	$98.84	5.578%	$104.3533	$104.35	$104.35	$104.40
Purchase #5	$114.60	3.405%	$118.5021	$118.50	$118.50	$118.50
Purchase #6	$167.97	8.823%	$182.79	$182.79	$182.80	$182.80
Purchase #7	$217.41	5.108%	$228.5153	$228.52	$228.50	$228.50
7 purchase totals =	$989.02		$1,049.4702	$1,049.47	$1,049.50	$1,049.50