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	$99.85	5.453%	$105.2948	$105.29	$105.30	$105.30
Purchase #2	$7.51	9.418%	$8.2173	$8.22	$8.20	$8.20
Purchase #3	$160.84	4.659%	$168.3335	$168.33	$168.35	$168.30
Purchase #4	$136.81	10.477%	$151.1436	$151.14	$151.15	$151.10
Purchase #5	$144.98	5.820%	$153.4178	$153.42	$153.40	$153.40
Purchase #6	$139.44	3.287%	$144.0234	$144.02	$144.00	$144.00
Purchase #7	$138.28	12.168%	$155.1059	$155.11	$155.10	$155.10
7 purchase totals =	$827.71		$885.5363	$885.53	$885.50	$885.40