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	$138.89	9.874%	$152.604	$152.60	$152.60	$152.60
Purchase #2	$238.70	6.756%	$254.8266	$254.83	$254.85	$254.80
Purchase #3	$162.49	11.643%	$181.4087	$181.41	$181.40	$181.40
Purchase #4	$159.76	3.834%	$165.8852	$165.89	$165.90	$165.90
Purchase #5	$250.90	5.698%	$265.1963	$265.20	$265.20	$265.20
Purchase #6	$139.27	12.582%	$156.793	$156.79	$156.80	$156.80
Purchase #7	$83.93	3.249%	$86.6569	$86.66	$86.65	$86.70
7 purchase totals =	$1,173.94		$1,263.3707	$1,263.38	$1,263.40	$1,263.40