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	$169.54	3.334%	$175.1925	$175.19	$175.20	$175.20
Purchase #2	$48.34	10.128%	$53.2359	$53.24	$53.25	$53.20
Purchase #3	$82.83	10.573%	$91.5876	$91.59	$91.60	$91.60
Purchase #4	$63.70	11.753%	$71.1867	$71.19	$71.20	$71.20
Purchase #5	$197.94	12.624%	$222.9279	$222.93	$222.95	$222.90
Purchase #6	$169.39	5.595%	$178.8674	$178.87	$178.85	$178.90
Purchase #7	$37.79	10.174%	$41.6348	$41.63	$41.65	$41.60
7 purchase totals =	$769.53		$834.6328	$834.64	$834.70	$834.60