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	$134.98	8.360%	$146.2643	$146.26	$146.25	$146.30
Purchase #2	$145.85	10.637%	$161.3641	$161.36	$161.35	$161.40
Purchase #3	$145.27	11.726%	$162.3044	$162.30	$162.30	$162.30
Purchase #4	$44.68	3.795%	$46.3756	$46.38	$46.40	$46.40
Purchase #5	$150.36	5.417%	$158.505	$158.51	$158.50	$158.50
Purchase #6	$74.80	5.434%	$78.8646	$78.86	$78.85	$78.90
Purchase #7	$218.48	13.260%	$247.4504	$247.45	$247.45	$247.50
7 purchase totals =	$914.42		$1,001.1284	$1,001.12	$1,001.10	$1,001.30