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	$47.96	9.557%	$52.5435	$52.54	$52.55	$52.50
Purchase #2	$243.96	11.230%	$271.3567	$271.36	$271.35	$271.40
Purchase #3	$148.38	4.506%	$155.066	$155.07	$155.05	$155.10
Purchase #4	$217.81	5.319%	$229.3953	$229.40	$229.40	$229.40
Purchase #5	$94.87	5.849%	$100.4189	$100.42	$100.40	$100.40
Purchase #6	$166.87	9.632%	$182.9429	$182.94	$182.95	$182.90
Purchase #7	$42.93	7.873%	$46.3099	$46.31	$46.30	$46.30
7 purchase totals =	$962.78		$1,038.0332	$1,038.04	$1,038.00	$1,038.00