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	$91.25	5.121%	$95.9229	$95.92	$95.90	$95.90
Purchase #2	$73.95	5.574%	$78.072	$78.07	$78.05	$78.10
Purchase #3	$44.85	9.622%	$49.1655	$49.17	$49.15	$49.20
Purchase #4	$72.98	7.579%	$78.5112	$78.51	$78.50	$78.50
Purchase #5	$63.43	9.748%	$69.6132	$69.61	$69.60	$69.60
Purchase #6	$163.59	6.755%	$174.6405	$174.64	$174.65	$174.60
Purchase #7	$236.97	12.444%	$266.4585	$266.46	$266.45	$266.50
7 purchase totals =	$747.02		$812.3838	$812.38	$812.30	$812.40