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	$250.53	12.843%	$282.7056	$282.71	$282.70	$282.70
Purchase #2	$100.31	6.865%	$107.1963	$107.20	$107.20	$107.20
Purchase #3	$209.26	4.453%	$218.5783	$218.58	$218.60	$218.60
Purchase #4	$41.87	13.190%	$47.3927	$47.39	$47.40	$47.40
Purchase #5	$54.65	12.538%	$61.502	$61.50	$61.50	$61.50
Purchase #6	$153.44	13.800%	$174.6147	$174.61	$174.60	$174.60
Purchase #7	$59.61	3.171%	$61.5002	$61.50	$61.50	$61.50
7 purchase totals =	$869.67		$953.4898	$953.49	$953.50	$953.50