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	$77.80	9.322%	$85.0525	$85.05	$85.05	$85.10
Purchase #2	$187.51	4.255%	$195.4886	$195.49	$195.50	$195.50
Purchase #3	$234.64	13.515%	$266.3516	$266.35	$266.35	$266.40
Purchase #4	$140.42	4.308%	$146.4693	$146.47	$146.45	$146.50
Purchase #5	$154.59	11.224%	$171.9412	$171.94	$171.95	$171.90
Purchase #6	$83.60	9.423%	$91.4776	$91.48	$91.50	$91.50
Purchase #7	$138.88	9.205%	$151.6639	$151.66	$151.65	$151.70
7 purchase totals =	$1,017.44		$1,108.4447	$1,108.44	$1,108.45	$1,108.60