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	$205.44	7.160%	$220.1495	$220.15	$220.15	$220.10
Purchase #2	$33.82	13.127%	$38.2596	$38.26	$38.25	$38.30
Purchase #3	$28.44	10.285%	$31.3651	$31.37	$31.35	$31.40
Purchase #4	$175.30	13.275%	$198.5711	$198.57	$198.55	$198.60
Purchase #5	$176.32	5.426%	$185.8871	$185.89	$185.90	$185.90
Purchase #6	$196.70	12.148%	$220.5951	$220.60	$220.60	$220.60
Purchase #7	$189.45	7.316%	$203.3102	$203.31	$203.30	$203.30
7 purchase totals =	$1,005.47		$1,098.1377	$1,098.15	$1,098.10	$1,098.20