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	$105.45	12.293%	$118.413	$118.41	$118.40	$118.40
Purchase #2	$27.89	11.298%	$31.041	$31.04	$31.05	$31.00
Purchase #3	$18.32	6.111%	$19.4395	$19.44	$19.45	$19.40
Purchase #4	$19.98	12.425%	$22.4625	$22.46	$22.45	$22.50
Purchase #5	$85.66	10.304%	$94.4864	$94.49	$94.50	$94.50
Purchase #6	$39.78	10.542%	$43.9736	$43.97	$43.95	$44.00
Purchase #7	$157.43	6.835%	$168.1903	$168.19	$168.20	$168.20
7 purchase totals =	$454.51		$498.0063	$498.00	$498.00	$498.00