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	$116.82	8.138%	$126.3268	$126.33	$126.35	$126.30
Purchase #2	$55.64	13.296%	$63.0379	$63.04	$63.05	$63.00
Purchase #3	$39.99	6.138%	$42.4446	$42.44	$42.45	$42.40
Purchase #4	$34.63	7.830%	$37.3415	$37.34	$37.35	$37.30
Purchase #5	$100.95	4.871%	$105.8673	$105.87	$105.85	$105.90
Purchase #6	$53.51	9.311%	$58.4923	$58.49	$58.50	$58.50
Purchase #7	$154.77	7.790%	$166.8266	$166.83	$166.85	$166.80
7 purchase totals =	$556.31		$600.3370	$600.34	$600.40	$600.20