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	$204.28	10.764%	$226.2687	$226.27	$226.25	$226.30
Purchase #2	$211.42	5.267%	$222.5555	$222.56	$222.55	$222.60
Purchase #3	$104.68	5.148%	$110.0689	$110.07	$110.05	$110.10
Purchase #4	$216.54	3.648%	$224.4394	$224.44	$224.45	$224.40
Purchase #5	$192.57	3.847%	$199.9782	$199.98	$200.00	$200.00
Purchase #6	$97.81	4.162%	$101.8809	$101.88	$101.90	$101.90
Purchase #7	$55.30	6.756%	$59.0361	$59.04	$59.05	$59.00
7 purchase totals =	$1,082.60		$1,144.2277	$1,144.24	$1,144.25	$1,144.30