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	$244.32	9.237%	$266.8878	$266.89	$266.90	$266.90
Purchase #2	$113.75	11.761%	$127.1281	$127.13	$127.15	$127.10
Purchase #3	$92.33	9.173%	$100.7994	$100.80	$100.80	$100.80
Purchase #4	$246.66	3.225%	$254.6148	$254.61	$254.60	$254.60
Purchase #5	$179.77	7.789%	$193.7723	$193.77	$193.75	$193.80
Purchase #6	$186.89	9.103%	$203.9026	$203.90	$203.90	$203.90
Purchase #7	$244.60	4.494%	$255.5923	$255.59	$255.60	$255.60
7 purchase totals =	$1,308.32		$1,402.6973	$1,402.69	$1,402.70	$1,402.70