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	$101.58	7.602%	$109.3021	$109.30	$109.30	$109.30
Purchase #2	$135.56	4.414%	$141.5436	$141.54	$141.55	$141.50
Purchase #3	$173.78	4.480%	$181.5653	$181.57	$181.55	$181.60
Purchase #4	$203.83	12.360%	$229.0234	$229.02	$229.00	$229.00
Purchase #5	$197.42	11.665%	$220.449	$220.45	$220.45	$220.40
Purchase #6	$158.72	6.649%	$169.2733	$169.27	$169.25	$169.30
Purchase #7	$175.96	3.741%	$182.5427	$182.54	$182.55	$182.50
7 purchase totals =	$1,146.85		$1,233.6994	$1,233.69	$1,233.65	$1,233.60