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	$189.76	8.132%	$205.1913	$205.19	$205.20	$205.20
Purchase #2	$170.41	7.628%	$183.4089	$183.41	$183.40	$183.40
Purchase #3	$171.74	10.248%	$189.3399	$189.34	$189.35	$189.30
Purchase #4	$138.31	7.502%	$148.686	$148.69	$148.70	$148.70
Purchase #5	$54.65	7.831%	$58.9296	$58.93	$58.95	$58.90
Purchase #6	$73.45	7.401%	$78.886	$78.89	$78.90	$78.90
Purchase #7	$70.60	11.615%	$78.8002	$78.80	$78.80	$78.80
7 purchase totals =	$868.92		$943.2419	$943.25	$943.30	$943.20