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	$66.95	9.516%	$73.321	$73.32	$73.30	$73.30
Purchase #2	$196.93	10.827%	$218.2516	$218.25	$218.25	$218.30
Purchase #3	$167.57	6.474%	$178.4185	$178.42	$178.40	$178.40
Purchase #4	$31.69	4.524%	$33.1237	$33.12	$33.10	$33.10
Purchase #5	$149.55	3.839%	$155.2912	$155.29	$155.30	$155.30
Purchase #6	$50.70	11.693%	$56.6284	$56.63	$56.65	$56.60
Purchase #7	$152.30	11.293%	$169.4992	$169.50	$169.50	$169.50
7 purchase totals =	$815.69		$884.5336	$884.53	$884.50	$884.50