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	$75.71	13.305%	$85.7832	$85.78	$85.80	$85.80
Purchase #2	$80.86	10.430%	$89.2937	$89.29	$89.30	$89.30
Purchase #3	$79.88	4.191%	$83.2278	$83.23	$83.25	$83.20
Purchase #4	$30.30	7.660%	$32.621	$32.62	$32.60	$32.60
Purchase #5	$40.57	9.253%	$44.3239	$44.32	$44.30	$44.30
Purchase #6	$52.98	13.745%	$60.2621	$60.26	$60.25	$60.30
Purchase #7	$117.77	10.426%	$130.0487	$130.05	$130.05	$130.00
7 purchase totals =	$478.07		$525.5604	$525.55	$525.55	$525.50