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	$154.74	9.659%	$169.6863	$169.69	$169.70	$169.70
Purchase #2	$186.60	4.589%	$195.1631	$195.16	$195.15	$195.20
Purchase #3	$37.56	12.207%	$42.1449	$42.14	$42.15	$42.10
Purchase #4	$52.83	3.175%	$54.5074	$54.51	$54.50	$54.50
Purchase #5	$200.91	4.283%	$209.515	$209.52	$209.50	$209.50
Purchase #6	$49.92	4.849%	$52.3406	$52.34	$52.35	$52.30
Purchase #7	$19.30	10.647%	$21.3549	$21.35	$21.35	$21.40
7 purchase totals =	$701.86		$744.7122	$744.71	$744.70	$744.70