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	$53.33	11.199%	$59.3024	$59.30	$59.30	$59.30
Purchase #2	$93.65	9.751%	$102.7818	$102.78	$102.80	$102.80
Purchase #3	$139.66	7.711%	$150.4292	$150.43	$150.45	$150.40
Purchase #4	$93.70	12.115%	$105.0518	$105.05	$105.05	$105.10
Purchase #5	$196.48	11.300%	$218.6822	$218.68	$218.70	$218.70
Purchase #6	$219.41	3.222%	$226.4794	$226.48	$226.50	$226.50
Purchase #7	$61.79	7.352%	$66.3328	$66.33	$66.35	$66.30
7 purchase totals =	$858.02		$929.0596	$929.05	$929.15	$929.10