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	$41.32	9.742%	$45.3454	$45.35	$45.35	$45.30
Purchase #2	$211.35	5.377%	$222.7143	$222.71	$222.70	$222.70
Purchase #3	$18.50	7.374%	$19.8642	$19.86	$19.85	$19.90
Purchase #4	$148.62	5.280%	$156.4671	$156.47	$156.45	$156.50
Purchase #5	$39.98	6.421%	$42.5471	$42.55	$42.55	$42.50
Purchase #6	$215.74	12.382%	$242.4529	$242.45	$242.45	$242.50
Purchase #7	$31.99	9.224%	$34.9408	$34.94	$34.95	$34.90
7 purchase totals =	$707.50		$764.3318	$764.33	$764.30	$764.30