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	$100.46	10.419%	$110.9269	$110.93	$110.95	$110.90
Purchase #2	$52.65	13.195%	$59.5972	$59.60	$59.60	$59.60
Purchase #3	$21.29	10.241%	$23.4703	$23.47	$23.45	$23.50
Purchase #4	$158.55	6.129%	$168.2675	$168.27	$168.25	$168.30
Purchase #5	$14.52	5.812%	$15.3639	$15.36	$15.35	$15.40
Purchase #6	$160.57	6.511%	$171.0247	$171.02	$171.00	$171.00
Purchase #7	$188.89	7.850%	$203.7179	$203.72	$203.70	$203.70
7 purchase totals =	$696.93		$752.3684	$752.37	$752.30	$752.40