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	$91.95	8.307%	$99.5883	$99.59	$99.60	$99.60
Purchase #2	$63.80	12.234%	$71.6053	$71.61	$71.60	$71.60
Purchase #3	$128.38	12.308%	$144.181	$144.18	$144.20	$144.20
Purchase #4	$16.48	8.355%	$17.8569	$17.86	$17.85	$17.90
Purchase #5	$41.35	3.406%	$42.7584	$42.76	$42.75	$42.80
Purchase #6	$34.63	10.550%	$38.2835	$38.28	$38.30	$38.30
Purchase #7	$34.43	6.560%	$36.6886	$36.69	$36.70	$36.70
7 purchase totals =	$411.02		$450.9620	$450.97	$451.00	$451.10