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	$190.56	7.211%	$204.3013	$204.30	$204.30	$204.30
Purchase #2	$207.87	11.411%	$231.59	$231.59	$231.60	$231.60
Purchase #3	$28.75	12.850%	$32.4444	$32.44	$32.45	$32.40
Purchase #4	$89.42	10.755%	$99.0371	$99.04	$99.05	$99.00
Purchase #5	$61.28	3.535%	$63.4462	$63.45	$63.45	$63.40
Purchase #6	$56.83	8.768%	$61.8129	$61.81	$61.80	$61.80
Purchase #7	$239.37	6.699%	$255.4054	$255.41	$255.40	$255.40
7 purchase totals =	$874.08		$948.0373	$948.04	$948.05	$947.90