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	$224.53	4.157%	$233.8637	$233.86	$233.85	$233.90
Purchase #2	$91.60	8.470%	$99.3585	$99.36	$99.35	$99.40
Purchase #3	$72.93	5.319%	$76.8091	$76.81	$76.80	$76.80
Purchase #4	$74.83	9.845%	$82.197	$82.20	$82.20	$82.20
Purchase #5	$177.61	9.404%	$194.3124	$194.31	$194.30	$194.30
Purchase #6	$9.29	10.667%	$10.281	$10.28	$10.30	$10.30
Purchase #7	$211.47	9.478%	$231.5131	$231.51	$231.50	$231.50
7 purchase totals =	$862.26		$928.3348	$928.33	$928.30	$928.40