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	$89.27	12.325%	$100.2725	$100.27	$100.25	$100.30
Purchase #2	$242.77	8.799%	$264.1313	$264.13	$264.15	$264.10
Purchase #3	$40.30	4.583%	$42.1469	$42.15	$42.15	$42.10
Purchase #4	$151.67	13.663%	$172.3927	$172.39	$172.40	$172.40
Purchase #5	$56.61	11.272%	$62.9911	$62.99	$63.00	$63.00
Purchase #6	$189.76	4.153%	$197.6407	$197.64	$197.65	$197.60
Purchase #7	$194.55	4.356%	$203.0246	$203.02	$203.00	$203.00
7 purchase totals =	$964.93		$1,042.5998	$1,042.59	$1,042.60	$1,042.50