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	$247.57	8.770%	$269.2819	$269.28	$269.30	$269.30
Purchase #2	$172.73	8.719%	$187.7903	$187.79	$187.80	$187.80
Purchase #3	$69.89	3.367%	$72.2432	$72.24	$72.25	$72.20
Purchase #4	$102.49	3.797%	$106.3815	$106.38	$106.40	$106.40
Purchase #5	$222.48	12.744%	$250.8329	$250.83	$250.85	$250.80
Purchase #6	$151.80	8.653%	$164.9353	$164.94	$164.95	$164.90
Purchase #7	$124.77	7.325%	$133.9094	$133.91	$133.90	$133.90
7 purchase totals =	$1,091.73		$1,185.3745	$1,185.37	$1,185.45	$1,185.30