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	$199.29	8.790%	$216.8076	$216.81	$216.80	$216.80
Purchase #2	$231.42	4.708%	$242.3153	$242.32	$242.30	$242.30
Purchase #3	$33.78	10.398%	$37.2924	$37.29	$37.30	$37.30
Purchase #4	$156.84	6.777%	$167.469	$167.47	$167.45	$167.50
Purchase #5	$28.97	8.814%	$31.5234	$31.52	$31.50	$31.50
Purchase #6	$142.79	8.531%	$154.9714	$154.97	$154.95	$155.00
Purchase #7	$232.50	11.600%	$259.47	$259.47	$259.45	$259.50
7 purchase totals =	$1,025.59		$1,109.8491	$1,109.85	$1,109.75	$1,109.90