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	$185.61	4.203%	$193.4112	$193.41	$193.40	$193.40
Purchase #2	$139.37	11.386%	$155.2387	$155.24	$155.25	$155.20
Purchase #3	$221.55	5.567%	$233.8837	$233.88	$233.90	$233.90
Purchase #4	$171.96	13.625%	$195.3896	$195.39	$195.40	$195.40
Purchase #5	$71.46	12.385%	$80.3103	$80.31	$80.30	$80.30
Purchase #6	$151.39	13.789%	$172.2652	$172.27	$172.25	$172.30
Purchase #7	$52.92	6.722%	$56.4773	$56.48	$56.50	$56.50
7 purchase totals =	$994.26		$1,086.9760	$1,086.98	$1,087.00	$1,087.00