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	$196.79	8.656%	$213.8241	$213.82	$213.80	$213.80
Purchase #2	$249.59	12.752%	$281.4177	$281.42	$281.40	$281.40
Purchase #3	$67.54	6.336%	$71.8193	$71.82	$71.80	$71.80
Purchase #4	$113.29	13.216%	$128.2624	$128.26	$128.25	$128.30
Purchase #5	$131.69	5.749%	$139.2609	$139.26	$139.25	$139.30
Purchase #6	$215.28	13.616%	$244.5925	$244.59	$244.60	$244.60
Purchase #7	$50.58	11.318%	$56.3046	$56.30	$56.30	$56.30
7 purchase totals =	$1,024.76		$1,135.4815	$1,135.47	$1,135.40	$1,135.50