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	$20.92	11.210%	$23.2651	$23.27	$23.25	$23.30
Purchase #2	$79.49	13.612%	$90.3102	$90.31	$90.30	$90.30
Purchase #3	$18.35	13.641%	$20.8531	$20.85	$20.85	$20.90
Purchase #4	$109.59	12.754%	$123.5671	$123.57	$123.55	$123.60
Purchase #5	$221.46	6.710%	$236.32	$236.32	$236.30	$236.30
Purchase #6	$144.41	11.437%	$160.9262	$160.93	$160.95	$160.90
Purchase #7	$200.54	3.204%	$206.9653	$206.97	$206.95	$207.00
7 purchase totals =	$794.76		$862.2070	$862.22	$862.15	$862.30