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	$31.48	5.663%	$33.2627	$33.26	$33.25	$33.30
Purchase #2	$128.86	13.839%	$146.6929	$146.69	$146.70	$146.70
Purchase #3	$14.57	5.339%	$15.3479	$15.35	$15.35	$15.30
Purchase #4	$63.77	3.170%	$65.7915	$65.79	$65.80	$65.80
Purchase #5	$71.97	5.643%	$76.0313	$76.03	$76.05	$76.00
Purchase #6	$51.39	4.846%	$53.8804	$53.88	$53.90	$53.90
Purchase #7	$176.32	5.181%	$185.4551	$185.46	$185.45	$185.50
7 purchase totals =	$538.36		$576.4618	$576.46	$576.50	$576.50