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	$46.27	7.132%	$49.57	$49.57	$49.55	$49.60
Purchase #2	$152.41	7.618%	$164.0206	$164.02	$164.00	$164.00
Purchase #3	$241.54	3.189%	$249.2427	$249.24	$249.25	$249.20
Purchase #4	$229.39	11.127%	$254.9142	$254.91	$254.90	$254.90
Purchase #5	$136.32	12.152%	$152.8856	$152.89	$152.90	$152.90
Purchase #6	$159.46	13.306%	$180.6777	$180.68	$180.70	$180.70
Purchase #7	$247.98	6.417%	$263.8929	$263.89	$263.90	$263.90
7 purchase totals =	$1,213.37		$1,315.2037	$1,315.20	$1,315.20	$1,315.20