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	$29.49	13.772%	$33.5514	$33.55	$33.55	$33.60
Purchase #2	$89.62	4.218%	$93.4002	$93.40	$93.40	$93.40
Purchase #3	$63.43	4.296%	$66.155	$66.16	$66.15	$66.20
Purchase #4	$138.32	3.211%	$142.7615	$142.76	$142.75	$142.80
Purchase #5	$99.33	7.282%	$106.5632	$106.56	$106.55	$106.60
Purchase #6	$220.29	11.845%	$246.3834	$246.38	$246.40	$246.40
Purchase #7	$94.54	6.173%	$100.376	$100.38	$100.40	$100.40
7 purchase totals =	$735.02		$789.1907	$789.19	$789.20	$789.40