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	$220.82	4.740%	$231.2869	$231.29	$231.30	$231.30
Purchase #2	$250.26	12.547%	$281.6601	$281.66	$281.65	$281.70
Purchase #3	$127.32	8.281%	$137.8634	$137.86	$137.85	$137.90
Purchase #4	$130.94	8.449%	$142.0031	$142.00	$142.00	$142.00
Purchase #5	$55.95	11.761%	$62.5303	$62.53	$62.55	$62.50
Purchase #6	$69.84	12.397%	$78.4981	$78.50	$78.50	$78.50
Purchase #7	$207.87	11.563%	$231.906	$231.91	$231.90	$231.90
7 purchase totals =	$1,063.00		$1,165.7479	$1,165.75	$1,165.75	$1,165.80