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	$57.81	6.837%	$61.7625	$61.76	$61.75	$61.80
Purchase #2	$77.29	11.425%	$86.1204	$86.12	$86.10	$86.10
Purchase #3	$134.74	8.814%	$146.616	$146.62	$146.60	$146.60
Purchase #4	$199.73	12.156%	$224.0092	$224.01	$224.00	$224.00
Purchase #5	$80.73	11.244%	$89.8073	$89.81	$89.80	$89.80
Purchase #6	$249.79	7.510%	$268.5492	$268.55	$268.55	$268.50
Purchase #7	$65.34	10.281%	$72.0576	$72.06	$72.05	$72.10
7 purchase totals =	$865.43		$948.9222	$948.93	$948.85	$948.90