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	$189.42	11.861%	$211.8871	$211.89	$211.90	$211.90
Purchase #2	$211.27	11.328%	$235.2027	$235.20	$235.20	$235.20
Purchase #3	$50.81	6.270%	$53.9958	$54.00	$54.00	$54.00
Purchase #4	$219.91	8.567%	$238.7497	$238.75	$238.75	$238.70
Purchase #5	$113.51	10.466%	$125.39	$125.39	$125.40	$125.40
Purchase #6	$217.64	7.254%	$233.4276	$233.43	$233.45	$233.40
Purchase #7	$49.40	6.459%	$52.5907	$52.59	$52.60	$52.60
7 purchase totals =	$1,051.96		$1,151.2436	$1,151.25	$1,151.30	$1,151.20