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	$183.28	9.491%	$200.6751	$200.68	$200.70	$200.70
Purchase #2	$32.90	4.340%	$34.3279	$34.33	$34.35	$34.30
Purchase #3	$28.74	7.499%	$30.8952	$30.90	$30.90	$30.90
Purchase #4	$117.29	8.790%	$127.5998	$127.60	$127.60	$127.60
Purchase #5	$29.96	6.437%	$31.8885	$31.89	$31.90	$31.90
Purchase #6	$93.79	13.644%	$106.5867	$106.59	$106.60	$106.60
Purchase #7	$26.64	10.288%	$29.3807	$29.38	$29.40	$29.40
7 purchase totals =	$512.60		$561.3539	$561.37	$561.45	$561.40