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	$13.49	4.839%	$14.1428	$14.14	$14.15	$14.10
Purchase #2	$82.79	9.777%	$90.8844	$90.88	$90.90	$90.90
Purchase #3	$233.28	12.758%	$263.0419	$263.04	$263.05	$263.00
Purchase #4	$209.73	3.485%	$217.0391	$217.04	$217.05	$217.00
Purchase #5	$174.49	5.420%	$183.9474	$183.95	$183.95	$183.90
Purchase #6	$126.28	12.738%	$142.3655	$142.37	$142.35	$142.40
Purchase #7	$128.88	8.197%	$139.4443	$139.44	$139.45	$139.40
7 purchase totals =	$968.94		$1,050.8654	$1,050.86	$1,050.90	$1,050.70