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	$81.26	5.143%	$85.4392	$85.44	$85.45	$85.40
Purchase #2	$187.59	13.217%	$212.3838	$212.38	$212.40	$212.40
Purchase #3	$250.34	5.725%	$264.672	$264.67	$264.65	$264.70
Purchase #4	$87.96	12.485%	$98.9418	$98.94	$98.95	$98.90
Purchase #5	$79.41	13.698%	$90.2876	$90.29	$90.30	$90.30
Purchase #6	$128.94	5.839%	$136.4688	$136.47	$136.45	$136.50
Purchase #7	$123.59	4.552%	$129.2158	$129.22	$129.20	$129.20
7 purchase totals =	$939.09		$1,017.4090	$1,017.41	$1,017.40	$1,017.40