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	$139.87	7.275%	$150.0455	$150.05	$150.05	$150.00
Purchase #2	$209.99	4.262%	$218.9398	$218.94	$218.95	$218.90
Purchase #3	$204.27	13.753%	$232.3633	$232.36	$232.35	$232.40
Purchase #4	$85.42	7.389%	$91.7317	$91.73	$91.75	$91.70
Purchase #5	$118.65	7.786%	$127.8881	$127.89	$127.90	$127.90
Purchase #6	$165.50	3.712%	$171.6434	$171.64	$171.65	$171.60
Purchase #7	$108.59	4.568%	$113.5504	$113.55	$113.55	$113.60
7 purchase totals =	$1,032.29		$1,106.1622	$1,106.16	$1,106.20	$1,106.10