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	$229.94	6.223%	$244.2492	$244.25	$244.25	$244.20
Purchase #2	$207.97	10.147%	$229.0727	$229.07	$229.05	$229.10
Purchase #3	$131.81	13.558%	$149.6808	$149.68	$149.70	$149.70
Purchase #4	$94.85	9.135%	$103.5145	$103.51	$103.50	$103.50
Purchase #5	$113.83	8.802%	$123.8493	$123.85	$123.85	$123.80
Purchase #6	$52.66	6.152%	$55.8996	$55.90	$55.90	$55.90
Purchase #7	$180.73	5.511%	$190.69	$190.69	$190.70	$190.70
7 purchase totals =	$1,011.79		$1,096.9561	$1,096.95	$1,096.95	$1,096.90