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	$119.71	6.297%	$127.2481	$127.25	$127.25	$127.20
Purchase #2	$240.61	9.203%	$262.7533	$262.75	$262.75	$262.80
Purchase #3	$27.73	9.852%	$30.462	$30.46	$30.45	$30.50
Purchase #4	$88.53	11.179%	$98.4268	$98.43	$98.45	$98.40
Purchase #5	$100.89	4.265%	$105.193	$105.19	$105.20	$105.20
Purchase #6	$69.88	4.134%	$72.7688	$72.77	$72.75	$72.80
Purchase #7	$230.63	12.674%	$259.86	$259.86	$259.85	$259.90
7 purchase totals =	$877.98		$956.7120	$956.71	$956.70	$956.80