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	$96.83	6.814%	$103.428	$103.43	$103.45	$103.40
Purchase #2	$47.47	3.567%	$49.1633	$49.16	$49.15	$49.20
Purchase #3	$164.28	4.590%	$171.8205	$171.82	$171.80	$171.80
Purchase #4	$152.25	13.549%	$172.8784	$172.88	$172.90	$172.90
Purchase #5	$196.77	7.713%	$211.9469	$211.95	$211.95	$211.90
Purchase #6	$131.35	13.694%	$149.3371	$149.34	$149.35	$149.30
Purchase #7	$177.90	11.253%	$197.9191	$197.92	$197.90	$197.90
7 purchase totals =	$966.85		$1,056.4933	$1,056.50	$1,056.50	$1,056.40