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	$165.69	10.633%	$183.3078	$183.31	$183.30	$183.30
Purchase #2	$230.47	10.601%	$254.9021	$254.90	$254.90	$254.90
Purchase #3	$29.75	12.369%	$33.4298	$33.43	$33.45	$33.40
Purchase #4	$197.32	6.656%	$210.4536	$210.45	$210.45	$210.50
Purchase #5	$50.53	4.202%	$52.6533	$52.65	$52.65	$52.70
Purchase #6	$172.28	5.172%	$181.1903	$181.19	$181.20	$181.20
Purchase #7	$155.38	8.863%	$169.1513	$169.15	$169.15	$169.20
7 purchase totals =	$1,001.42		$1,085.0882	$1,085.08	$1,085.10	$1,085.20