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	$65.49	5.227%	$68.9132	$68.91	$68.90	$68.90
Purchase #2	$102.98	12.780%	$116.1408	$116.14	$116.15	$116.10
Purchase #3	$90.56	10.859%	$100.3939	$100.39	$100.40	$100.40
Purchase #4	$157.91	6.133%	$167.5946	$167.59	$167.60	$167.60
Purchase #5	$185.83	8.795%	$202.1737	$202.17	$202.15	$202.20
Purchase #6	$139.72	10.846%	$154.874	$154.87	$154.85	$154.90
Purchase #7	$120.47	6.467%	$128.2608	$128.26	$128.25	$128.30
7 purchase totals =	$862.96		$938.3510	$938.33	$938.30	$938.40