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	$145.59	4.568%	$152.2406	$152.24	$152.25	$152.20
Purchase #2	$131.60	11.326%	$146.505	$146.51	$146.50	$146.50
Purchase #3	$197.64	13.792%	$224.8985	$224.90	$224.90	$224.90
Purchase #4	$194.59	8.729%	$211.5758	$211.58	$211.60	$211.60
Purchase #5	$68.55	3.727%	$71.1049	$71.10	$71.10	$71.10
Purchase #6	$123.42	6.439%	$131.367	$131.37	$131.35	$131.40
Purchase #7	$177.42	10.559%	$196.1538	$196.15	$196.15	$196.20
7 purchase totals =	$1,038.81		$1,133.8456	$1,133.85	$1,133.85	$1,133.90