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	$237.75	12.545%	$267.5757	$267.58	$267.60	$267.60
Purchase #2	$239.31	4.597%	$250.3111	$250.31	$250.30	$250.30
Purchase #3	$182.30	8.567%	$197.9176	$197.92	$197.90	$197.90
Purchase #4	$96.89	13.107%	$109.5894	$109.59	$109.60	$109.60
Purchase #5	$102.95	8.442%	$111.641	$111.64	$111.65	$111.60
Purchase #6	$231.33	7.696%	$249.1332	$249.13	$249.15	$249.10
Purchase #7	$34.85	13.302%	$39.4857	$39.49	$39.50	$39.50
7 purchase totals =	$1,125.38		$1,225.6537	$1,225.66	$1,225.70	$1,225.60