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	$234.73	7.734%	$252.884	$252.88	$252.90	$252.90
Purchase #2	$85.45	4.177%	$89.0192	$89.02	$89.00	$89.00
Purchase #3	$191.26	13.754%	$217.5659	$217.57	$217.55	$217.60
Purchase #4	$86.74	3.606%	$89.8678	$89.87	$89.85	$89.90
Purchase #5	$8.60	10.739%	$9.5236	$9.52	$9.50	$9.50
Purchase #6	$184.27	6.860%	$196.9109	$196.91	$196.90	$196.90
Purchase #7	$212.55	3.677%	$220.3655	$220.37	$220.35	$220.40
7 purchase totals =	$1,003.60		$1,076.1369	$1,076.14	$1,076.05	$1,076.20