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	$218.55	7.443%	$234.8167	$234.82	$234.80	$234.80
Purchase #2	$6.56	8.724%	$7.1323	$7.13	$7.15	$7.10
Purchase #3	$53.50	13.404%	$60.6711	$60.67	$60.65	$60.70
Purchase #4	$151.93	10.534%	$167.9343	$167.93	$167.95	$167.90
Purchase #5	$27.90	5.332%	$29.3876	$29.39	$29.40	$29.40
Purchase #6	$160.71	12.854%	$181.3677	$181.37	$181.35	$181.40
Purchase #7	$74.53	10.802%	$82.5807	$82.58	$82.60	$82.60
7 purchase totals =	$693.68		$763.8904	$763.89	$763.90	$763.90