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	$104.41	11.391%	$116.3033	$116.30	$116.30	$116.30
Purchase #2	$235.60	11.798%	$263.3961	$263.40	$263.40	$263.40
Purchase #3	$65.30	9.632%	$71.5897	$71.59	$71.60	$71.60
Purchase #4	$176.95	3.839%	$183.7431	$183.74	$183.75	$183.70
Purchase #5	$36.33	11.363%	$40.4582	$40.46	$40.45	$40.50
Purchase #6	$181.40	7.500%	$195.005	$195.01	$195.00	$195.00
Purchase #7	$167.46	13.846%	$190.6465	$190.65	$190.65	$190.60
7 purchase totals =	$967.45		$1,061.1419	$1,061.15	$1,061.15	$1,061.10