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	$137.43	4.460%	$143.5594	$143.56	$143.55	$143.60
Purchase #2	$93.39	3.674%	$96.8211	$96.82	$96.80	$96.80
Purchase #3	$190.61	11.374%	$212.29	$212.29	$212.30	$212.30
Purchase #4	$17.55	12.639%	$19.7681	$19.77	$19.75	$19.80
Purchase #5	$226.59	11.786%	$253.2959	$253.30	$253.30	$253.30
Purchase #6	$110.67	5.145%	$116.364	$116.36	$116.35	$116.40
Purchase #7	$119.25	10.270%	$131.497	$131.50	$131.50	$131.50
7 purchase totals =	$895.49		$973.5955	$973.60	$973.55	$973.70