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	$11.47	3.578%	$11.8804	$11.88	$11.90	$11.90
Purchase #2	$61.27	6.405%	$65.1943	$65.19	$65.20	$65.20
Purchase #3	$104.46	8.610%	$113.454	$113.45	$113.45	$113.50
Purchase #4	$154.80	6.443%	$164.7738	$164.77	$164.75	$164.80
Purchase #5	$55.73	13.579%	$63.2976	$63.30	$63.30	$63.30
Purchase #6	$249.69	7.859%	$269.3131	$269.31	$269.30	$269.30
Purchase #7	$41.47	11.328%	$46.1677	$46.17	$46.15	$46.20
7 purchase totals =	$678.89		$734.0809	$734.07	$734.05	$734.20