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	$184.41	13.802%	$209.8623	$209.86	$209.85	$209.90
Purchase #2	$214.92	7.728%	$231.529	$231.53	$231.55	$231.50
Purchase #3	$7.96	6.851%	$8.5053	$8.51	$8.50	$8.50
Purchase #4	$164.71	12.634%	$185.5195	$185.52	$185.50	$185.50
Purchase #5	$174.97	6.872%	$186.9939	$186.99	$187.00	$187.00
Purchase #6	$31.52	3.522%	$32.6301	$32.63	$32.65	$32.60
Purchase #7	$120.91	5.630%	$127.7172	$127.72	$127.70	$127.70
7 purchase totals =	$899.40		$982.7573	$982.76	$982.75	$982.70