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	$195.29	8.571%	$212.0283	$212.03	$212.05	$212.00
Purchase #2	$223.31	12.371%	$250.9357	$250.94	$250.95	$250.90
Purchase #3	$238.96	8.403%	$259.0398	$259.04	$259.05	$259.00
Purchase #4	$78.69	8.597%	$85.455	$85.46	$85.45	$85.50
Purchase #5	$93.59	6.365%	$99.547	$99.55	$99.55	$99.50
Purchase #6	$177.47	4.543%	$185.5325	$185.53	$185.55	$185.50
Purchase #7	$229.30	7.693%	$246.94	$246.94	$246.95	$246.90
7 purchase totals =	$1,236.61		$1,339.4783	$1,339.49	$1,339.55	$1,339.30