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	$76.82	6.827%	$82.0645	$82.06	$82.05	$82.10
Purchase #2	$183.61	4.736%	$192.3058	$192.31	$192.30	$192.30
Purchase #3	$117.37	5.721%	$124.0847	$124.08	$124.10	$124.10
Purchase #4	$104.87	11.480%	$116.9091	$116.91	$116.90	$116.90
Purchase #5	$79.92	8.513%	$86.7236	$86.72	$86.70	$86.70
Purchase #6	$216.82	4.719%	$227.0517	$227.05	$227.05	$227.10
Purchase #7	$131.57	11.131%	$146.2151	$146.22	$146.20	$146.20
7 purchase totals =	$910.98		$975.3545	$975.35	$975.30	$975.40