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	$89.74	12.479%	$100.9387	$100.94	$100.95	$100.90
Purchase #2	$220.32	11.719%	$246.1393	$246.14	$246.15	$246.10
Purchase #3	$99.75	9.752%	$109.4776	$109.48	$109.50	$109.50
Purchase #4	$54.63	8.151%	$59.0829	$59.08	$59.10	$59.10
Purchase #5	$144.69	3.189%	$149.3042	$149.30	$149.30	$149.30
Purchase #6	$14.30	4.543%	$14.9496	$14.95	$14.95	$14.90
Purchase #7	$75.42	8.103%	$81.5313	$81.53	$81.55	$81.50
7 purchase totals =	$698.85		$761.4236	$761.42	$761.50	$761.30