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	$153.28	3.108%	$158.0439	$158.04	$158.05	$158.00
Purchase #2	$134.59	6.196%	$142.9292	$142.93	$142.95	$142.90
Purchase #3	$5.72	10.423%	$6.3162	$6.32	$6.30	$6.30
Purchase #4	$177.54	4.472%	$185.4796	$185.48	$185.50	$185.50
Purchase #5	$85.43	12.813%	$96.3761	$96.38	$96.40	$96.40
Purchase #6	$68.56	5.603%	$72.4014	$72.40	$72.40	$72.40
Purchase #7	$160.79	5.559%	$169.7283	$169.73	$169.75	$169.70
7 purchase totals =	$785.91		$831.2747	$831.28	$831.35	$831.20