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	$213.74	5.302%	$225.0725	$225.07	$225.05	$225.10
Purchase #2	$192.32	9.769%	$211.1077	$211.11	$211.10	$211.10
Purchase #3	$120.42	6.264%	$127.9631	$127.96	$127.95	$128.00
Purchase #4	$36.73	11.402%	$40.918	$40.92	$40.90	$40.90
Purchase #5	$176.56	6.417%	$187.8899	$187.89	$187.90	$187.90
Purchase #6	$111.42	4.226%	$116.1286	$116.13	$116.15	$116.10
Purchase #7	$161.31	8.739%	$175.4069	$175.41	$175.40	$175.40
7 purchase totals =	$1,012.50		$1,084.4867	$1,084.49	$1,084.45	$1,084.50