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	$74.34	5.429%	$78.3759	$78.38	$78.40	$78.40
Purchase #2	$79.53	7.800%	$85.7333	$85.73	$85.75	$85.70
Purchase #3	$78.61	4.499%	$82.1467	$82.15	$82.15	$82.10
Purchase #4	$79.50	7.449%	$85.422	$85.42	$85.40	$85.40
Purchase #5	$166.29	7.364%	$178.5356	$178.54	$178.55	$178.50
Purchase #6	$95.51	6.365%	$101.5892	$101.59	$101.60	$101.60
Purchase #7	$103.93	10.310%	$114.6452	$114.65	$114.65	$114.60
7 purchase totals =	$677.71		$726.4479	$726.46	$726.50	$726.30