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	$215.43	11.744%	$240.7301	$240.73	$240.75	$240.70
Purchase #2	$79.27	12.286%	$89.0091	$89.01	$89.00	$89.00
Purchase #3	$244.64	6.504%	$260.5514	$260.55	$260.55	$260.60
Purchase #4	$238.32	3.175%	$245.8867	$245.89	$245.90	$245.90
Purchase #5	$53.85	12.517%	$60.5904	$60.59	$60.60	$60.60
Purchase #6	$155.78	11.352%	$173.4641	$173.46	$173.45	$173.50
Purchase #7	$205.60	11.661%	$229.575	$229.58	$229.60	$229.60
7 purchase totals =	$1,192.89		$1,299.8068	$1,299.81	$1,299.85	$1,299.90