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	$187.63	12.623%	$211.3145	$211.31	$211.30	$211.30
Purchase #2	$96.64	13.385%	$109.5753	$109.58	$109.60	$109.60
Purchase #3	$75.69	13.720%	$86.0747	$86.07	$86.05	$86.10
Purchase #4	$138.69	7.144%	$148.598	$148.60	$148.60	$148.60
Purchase #5	$237.74	5.401%	$250.5803	$250.58	$250.60	$250.60
Purchase #6	$161.76	4.354%	$168.803	$168.80	$168.80	$168.80
Purchase #7	$187.93	11.450%	$209.448	$209.45	$209.45	$209.40
7 purchase totals =	$1,086.08		$1,184.3938	$1,184.39	$1,184.40	$1,184.40