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	$219.41	12.134%	$246.0332	$246.03	$246.05	$246.00
Purchase #2	$134.98	11.369%	$150.3259	$150.33	$150.35	$150.30
Purchase #3	$133.85	13.592%	$152.0429	$152.04	$152.05	$152.00
Purchase #4	$52.72	12.208%	$59.1561	$59.16	$59.15	$59.20
Purchase #5	$49.82	9.307%	$54.4567	$54.46	$54.45	$54.50
Purchase #6	$197.82	12.694%	$222.9313	$222.93	$222.95	$222.90
Purchase #7	$200.88	9.658%	$220.281	$220.28	$220.30	$220.30
7 purchase totals =	$989.48		$1,105.2271	$1,105.23	$1,105.30	$1,105.20