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	$118.87	8.430%	$128.8907	$128.89	$128.90	$128.90
Purchase #2	$111.54	13.839%	$126.976	$126.98	$127.00	$127.00
Purchase #3	$98.32	11.367%	$109.496	$109.50	$109.50	$109.50
Purchase #4	$187.36	13.171%	$212.0372	$212.04	$212.05	$212.00
Purchase #5	$44.64	10.847%	$49.4821	$49.48	$49.50	$49.50
Purchase #6	$250.53	8.157%	$270.9657	$270.97	$270.95	$271.00
Purchase #7	$143.87	4.619%	$150.5154	$150.52	$150.50	$150.50
7 purchase totals =	$955.13		$1,048.3631	$1,048.38	$1,048.40	$1,048.40