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	$198.65	11.216%	$220.9306	$220.93	$220.95	$220.90
Purchase #2	$85.67	6.558%	$91.2882	$91.29	$91.30	$91.30
Purchase #3	$39.38	10.158%	$43.3802	$43.38	$43.40	$43.40
Purchase #4	$201.78	13.496%	$229.0122	$229.01	$229.00	$229.00
Purchase #5	$32.69	3.670%	$33.8897	$33.89	$33.90	$33.90
Purchase #6	$246.37	7.686%	$265.306	$265.31	$265.30	$265.30
Purchase #7	$180.77	10.518%	$199.7834	$199.78	$199.80	$199.80
7 purchase totals =	$985.31		$1,083.5903	$1,083.59	$1,083.65	$1,083.60