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	$178.43	11.505%	$198.9584	$198.96	$198.95	$199.00
Purchase #2	$41.53	9.205%	$45.3528	$45.35	$45.35	$45.40
Purchase #3	$162.60	12.516%	$182.951	$182.95	$182.95	$183.00
Purchase #4	$124.40	12.800%	$140.3232	$140.32	$140.30	$140.30
Purchase #5	$51.41	7.701%	$55.3691	$55.37	$55.35	$55.40
Purchase #6	$151.29	3.420%	$156.4641	$156.46	$156.45	$156.50
Purchase #7	$158.46	4.512%	$165.6097	$165.61	$165.60	$165.60
7 purchase totals =	$868.12		$945.0283	$945.02	$944.95	$945.20