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	$150.52	7.820%	$162.2907	$162.29	$162.30	$162.30
Purchase #2	$152.79	7.496%	$164.2431	$164.24	$164.25	$164.20
Purchase #3	$18.29	7.763%	$19.7099	$19.71	$19.70	$19.70
Purchase #4	$84.28	5.849%	$89.2095	$89.21	$89.20	$89.20
Purchase #5	$163.73	6.531%	$174.4232	$174.42	$174.40	$174.40
Purchase #6	$223.51	11.592%	$249.4193	$249.42	$249.40	$249.40
Purchase #7	$229.80	4.572%	$240.3065	$240.31	$240.30	$240.30
7 purchase totals =	$1,022.92		$1,099.6022	$1,099.60	$1,099.55	$1,099.50