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	$90.52	9.241%	$98.885	$98.89	$98.90	$98.90
Purchase #2	$29.68	8.160%	$32.1019	$32.10	$32.10	$32.10
Purchase #3	$94.74	5.184%	$99.6513	$99.65	$99.65	$99.70
Purchase #4	$70.35	11.387%	$78.3608	$78.36	$78.35	$78.40
Purchase #5	$146.86	8.207%	$158.9128	$158.91	$158.90	$158.90
Purchase #6	$175.48	12.548%	$197.4992	$197.50	$197.50	$197.50
Purchase #7	$106.50	8.478%	$115.5291	$115.53	$115.55	$115.50
7 purchase totals =	$714.13		$780.9401	$780.94	$780.95	$781.00