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	$118.63	8.164%	$128.315	$128.32	$128.30	$128.30
Purchase #2	$40.85	11.712%	$45.6344	$45.63	$45.65	$45.60
Purchase #3	$136.53	11.186%	$151.8022	$151.80	$151.80	$151.80
Purchase #4	$210.53	5.168%	$221.4102	$221.41	$221.40	$221.40
Purchase #5	$153.90	9.869%	$169.0884	$169.09	$169.10	$169.10
Purchase #6	$93.83	7.252%	$100.6346	$100.63	$100.65	$100.60
Purchase #7	$238.93	12.400%	$268.5573	$268.56	$268.55	$268.60
7 purchase totals =	$993.20		$1,085.4421	$1,085.44	$1,085.45	$1,085.40