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	$81.63	8.869%	$88.8698	$88.87	$88.85	$88.90
Purchase #2	$74.81	3.109%	$77.1358	$77.14	$77.15	$77.10
Purchase #3	$101.97	9.451%	$111.6072	$111.61	$111.60	$111.60
Purchase #4	$165.49	6.694%	$176.5679	$176.57	$176.55	$176.60
Purchase #5	$79.34	4.134%	$82.6199	$82.62	$82.60	$82.60
Purchase #6	$176.57	12.470%	$198.5883	$198.59	$198.60	$198.60
Purchase #7	$199.30	7.820%	$214.8853	$214.89	$214.90	$214.90
7 purchase totals =	$879.11		$950.2742	$950.29	$950.25	$950.30