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	$191.33	11.591%	$213.5071	$213.51	$213.50	$213.50
Purchase #2	$21.83	4.858%	$22.8905	$22.89	$22.90	$22.90
Purchase #3	$169.57	8.402%	$183.8173	$183.82	$183.80	$183.80
Purchase #4	$235.56	7.526%	$253.2882	$253.29	$253.30	$253.30
Purchase #5	$19.83	6.243%	$21.068	$21.07	$21.05	$21.10
Purchase #6	$124.86	5.407%	$131.6112	$131.61	$131.60	$131.60
Purchase #7	$28.28	13.119%	$31.9901	$31.99	$32.00	$32.00
7 purchase totals =	$791.26		$858.1724	$858.18	$858.15	$858.20