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	$193.38	7.323%	$207.5412	$207.54	$207.55	$207.50
Purchase #2	$241.71	13.608%	$274.6019	$274.60	$274.60	$274.60
Purchase #3	$42.64	10.517%	$47.1244	$47.12	$47.10	$47.10
Purchase #4	$13.69	5.610%	$14.458	$14.46	$14.45	$14.50
Purchase #5	$41.77	13.748%	$47.5125	$47.51	$47.50	$47.50
Purchase #6	$145.72	10.430%	$160.9186	$160.92	$160.90	$160.90
Purchase #7	$134.42	13.412%	$152.4484	$152.45	$152.45	$152.40
7 purchase totals =	$813.33		$904.6050	$904.60	$904.55	$904.50