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	$239.46	13.770%	$272.4336	$272.43	$272.45	$272.40
Purchase #2	$28.77	10.240%	$31.716	$31.72	$31.70	$31.70
Purchase #3	$144.92	7.132%	$155.2557	$155.26	$155.25	$155.30
Purchase #4	$193.31	7.280%	$207.383	$207.38	$207.40	$207.40
Purchase #5	$17.76	12.305%	$19.9454	$19.95	$19.95	$19.90
Purchase #6	$75.47	4.218%	$78.6533	$78.65	$78.65	$78.70
Purchase #7	$225.84	5.435%	$238.1144	$238.11	$238.10	$238.10
7 purchase totals =	$925.53		$1,003.5014	$1,003.50	$1,003.50	$1,003.50