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	$219.46	6.432%	$233.5757	$233.58	$233.60	$233.60
Purchase #2	$196.38	11.628%	$219.2151	$219.22	$219.20	$219.20
Purchase #3	$173.52	3.752%	$180.0305	$180.03	$180.05	$180.00
Purchase #4	$29.89	10.718%	$33.0936	$33.09	$33.10	$33.10
Purchase #5	$114.99	12.365%	$129.2085	$129.21	$129.20	$129.20
Purchase #6	$101.34	9.656%	$111.1254	$111.13	$111.15	$111.10
Purchase #7	$196.54	4.285%	$204.9617	$204.96	$204.95	$205.00
7 purchase totals =	$1,032.12		$1,111.2105	$1,111.22	$1,111.25	$1,111.20