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	$49.77	6.229%	$52.8702	$52.87	$52.85	$52.90
Purchase #2	$205.93	13.267%	$233.2507	$233.25	$233.25	$233.30
Purchase #3	$10.38	9.253%	$11.3405	$11.34	$11.35	$11.30
Purchase #4	$114.26	9.681%	$125.3215	$125.32	$125.30	$125.30
Purchase #5	$237.92	11.136%	$264.4148	$264.41	$264.40	$264.40
Purchase #6	$14.51	13.724%	$16.5014	$16.50	$16.50	$16.50
Purchase #7	$127.37	3.549%	$131.8904	$131.89	$131.90	$131.90
7 purchase totals =	$760.14		$835.5895	$835.58	$835.55	$835.60