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	$166.25	7.249%	$178.3015	$178.30	$178.30	$178.30
Purchase #2	$21.91	10.525%	$24.216	$24.22	$24.20	$24.20
Purchase #3	$35.55	3.670%	$36.8547	$36.85	$36.85	$36.90
Purchase #4	$82.37	3.472%	$85.2299	$85.23	$85.25	$85.20
Purchase #5	$242.96	8.407%	$263.3856	$263.39	$263.40	$263.40
Purchase #6	$71.74	13.631%	$81.5189	$81.52	$81.50	$81.50
Purchase #7	$33.55	10.322%	$37.013	$37.01	$37.00	$37.00
7 purchase totals =	$654.33		$706.5196	$706.52	$706.50	$706.50