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	$146.88	10.349%	$162.0806	$162.08	$162.10	$162.10
Purchase #2	$44.37	8.277%	$48.0425	$48.04	$48.05	$48.00
Purchase #3	$224.71	11.785%	$251.1921	$251.19	$251.20	$251.20
Purchase #4	$157.73	12.562%	$177.544	$177.54	$177.55	$177.50
Purchase #5	$85.36	4.587%	$89.2755	$89.28	$89.30	$89.30
Purchase #6	$240.80	11.224%	$267.8274	$267.83	$267.85	$267.80
Purchase #7	$85.52	6.113%	$90.7478	$90.75	$90.75	$90.70
7 purchase totals =	$985.37		$1,086.7099	$1,086.71	$1,086.80	$1,086.60