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	$100.48	8.585%	$109.1062	$109.11	$109.10	$109.10
Purchase #2	$226.68	12.379%	$254.7407	$254.74	$254.75	$254.70
Purchase #3	$147.61	3.268%	$152.4339	$152.43	$152.45	$152.40
Purchase #4	$27.49	9.534%	$30.1109	$30.11	$30.10	$30.10
Purchase #5	$226.94	5.292%	$238.9497	$238.95	$238.95	$238.90
Purchase #6	$234.89	3.840%	$243.9098	$243.91	$243.90	$243.90
Purchase #7	$66.36	9.150%	$72.4319	$72.43	$72.45	$72.40
7 purchase totals =	$1,030.45		$1,101.6831	$1,101.68	$1,101.70	$1,101.50