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	$102.79	11.675%	$114.7907	$114.79	$114.80	$114.80
Purchase #2	$28.32	12.862%	$31.9625	$31.96	$31.95	$32.00
Purchase #3	$30.39	6.281%	$32.2988	$32.30	$32.30	$32.30
Purchase #4	$34.25	10.770%	$37.9387	$37.94	$37.95	$37.90
Purchase #5	$219.39	8.792%	$238.6788	$238.68	$238.70	$238.70
Purchase #6	$18.65	6.104%	$19.7884	$19.79	$19.80	$19.80
Purchase #7	$59.43	5.457%	$62.6731	$62.67	$62.65	$62.70
7 purchase totals =	$493.22		$538.1310	$538.13	$538.15	$538.20