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	$85.85	11.212%	$95.4755	$95.48	$95.50	$95.50
Purchase #2	$140.99	6.248%	$149.7991	$149.80	$149.80	$149.80
Purchase #3	$128.32	12.667%	$144.5743	$144.57	$144.55	$144.60
Purchase #4	$136.91	13.687%	$155.6489	$155.65	$155.65	$155.60
Purchase #5	$140.31	7.306%	$150.561	$150.56	$150.55	$150.60
Purchase #6	$143.66	5.280%	$151.2452	$151.25	$151.25	$151.20
Purchase #7	$131.29	11.808%	$146.7927	$146.79	$146.80	$146.80
7 purchase totals =	$907.33		$994.0967	$994.10	$994.10	$994.10