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	$239.81	12.552%	$269.911	$269.91	$269.90	$269.90
Purchase #2	$80.69	11.123%	$89.6651	$89.67	$89.65	$89.70
Purchase #3	$143.47	12.501%	$161.4052	$161.41	$161.40	$161.40
Purchase #4	$29.54	13.292%	$33.4665	$33.47	$33.45	$33.50
Purchase #5	$107.79	11.792%	$120.5006	$120.50	$120.50	$120.50
Purchase #6	$143.58	6.212%	$152.4992	$152.50	$152.50	$152.50
Purchase #7	$195.44	4.798%	$204.8172	$204.82	$204.80	$204.80
7 purchase totals =	$940.32		$1,032.2648	$1,032.28	$1,032.20	$1,032.30