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	$83.53	9.745%	$91.67	$91.67	$91.65	$91.70
Purchase #2	$66.40	10.707%	$73.5094	$73.51	$73.50	$73.50
Purchase #3	$201.97	3.163%	$208.3583	$208.36	$208.35	$208.40
Purchase #4	$45.48	3.611%	$47.1223	$47.12	$47.10	$47.10
Purchase #5	$46.61	13.506%	$52.9051	$52.91	$52.90	$52.90
Purchase #6	$73.33	12.839%	$82.7448	$82.74	$82.75	$82.70
Purchase #7	$63.71	13.418%	$72.2586	$72.26	$72.25	$72.30
7 purchase totals =	$581.03		$628.5685	$628.57	$628.50	$628.60