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	$98.56	3.111%	$101.6262	$101.63	$101.65	$101.60
Purchase #2	$139.33	8.437%	$151.0853	$151.09	$151.10	$151.10
Purchase #3	$219.31	3.759%	$227.5539	$227.55	$227.55	$227.60
Purchase #4	$123.36	6.603%	$131.5055	$131.51	$131.50	$131.50
Purchase #5	$145.43	10.613%	$160.8645	$160.86	$160.85	$160.90
Purchase #6	$124.91	7.570%	$134.3657	$134.37	$134.35	$134.40
Purchase #7	$51.81	9.624%	$56.7962	$56.80	$56.80	$56.80
7 purchase totals =	$902.71		$963.7973	$963.81	$963.80	$963.90