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	$93.76	12.612%	$105.585	$105.59	$105.60	$105.60
Purchase #2	$79.84	4.792%	$83.6659	$83.67	$83.65	$83.70
Purchase #3	$31.86	3.467%	$32.9646	$32.96	$32.95	$33.00
Purchase #4	$56.86	9.476%	$62.2481	$62.25	$62.25	$62.20
Purchase #5	$180.40	3.552%	$186.8078	$186.81	$186.80	$186.80
Purchase #6	$19.64	4.782%	$20.5792	$20.58	$20.60	$20.60
Purchase #7	$38.71	4.416%	$40.4194	$40.42	$40.40	$40.40
7 purchase totals =	$501.07		$532.2700	$532.28	$532.25	$532.30