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	$194.48	11.269%	$216.396	$216.40	$216.40	$216.40
Purchase #2	$242.58	3.168%	$250.2649	$250.26	$250.25	$250.30
Purchase #3	$84.95	6.435%	$90.4165	$90.42	$90.40	$90.40
Purchase #4	$168.38	6.305%	$178.9964	$179.00	$179.00	$179.00
Purchase #5	$45.78	8.779%	$49.799	$49.80	$49.80	$49.80
Purchase #6	$197.78	3.846%	$205.3866	$205.39	$205.40	$205.40
Purchase #7	$217.94	11.366%	$242.7111	$242.71	$242.70	$242.70
7 purchase totals =	$1,151.89		$1,233.9705	$1,233.98	$1,233.95	$1,234.00