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	$19.76	11.673%	$22.0666	$22.07	$22.05	$22.10
Purchase #2	$148.94	10.460%	$164.5191	$164.52	$164.50	$164.50
Purchase #3	$95.74	12.355%	$107.5687	$107.57	$107.55	$107.60
Purchase #4	$228.50	11.642%	$255.102	$255.10	$255.10	$255.10
Purchase #5	$137.68	10.327%	$151.8982	$151.90	$151.90	$151.90
Purchase #6	$156.27	8.725%	$169.9046	$169.90	$169.90	$169.90
Purchase #7	$173.51	11.529%	$193.514	$193.51	$193.50	$193.50
7 purchase totals =	$960.40		$1,064.5732	$1,064.57	$1,064.50	$1,064.60