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	$142.43	6.431%	$151.5897	$151.59	$151.60	$151.60
Purchase #2	$33.91	12.193%	$38.0446	$38.04	$38.05	$38.00
Purchase #3	$125.38	8.481%	$136.0135	$136.01	$136.00	$136.00
Purchase #4	$19.36	11.207%	$21.5297	$21.53	$21.55	$21.50
Purchase #5	$57.60	7.591%	$61.9724	$61.97	$61.95	$62.00
Purchase #6	$171.79	6.420%	$182.8189	$182.82	$182.80	$182.80
Purchase #7	$99.54	6.417%	$105.9275	$105.93	$105.95	$105.90
7 purchase totals =	$650.01		$697.8963	$697.89	$697.90	$697.80