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	$206.37	7.838%	$222.5453	$222.55	$222.55	$222.50
Purchase #2	$17.73	8.409%	$19.2209	$19.22	$19.20	$19.20
Purchase #3	$54.48	11.535%	$60.7643	$60.76	$60.75	$60.80
Purchase #4	$67.29	5.852%	$71.2278	$71.23	$71.25	$71.20
Purchase #5	$99.85	12.560%	$112.3912	$112.39	$112.40	$112.40
Purchase #6	$83.58	6.800%	$89.2634	$89.26	$89.25	$89.30
Purchase #7	$80.46	5.560%	$84.9336	$84.93	$84.95	$84.90
7 purchase totals =	$609.76		$660.3465	$660.34	$660.35	$660.30