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	$127.77	9.132%	$139.438	$139.44	$139.45	$139.40
Purchase #2	$211.45	13.813%	$240.6576	$240.66	$240.65	$240.70
Purchase #3	$160.75	4.515%	$168.0079	$168.01	$168.00	$168.00
Purchase #4	$91.56	5.804%	$96.8741	$96.87	$96.85	$96.90
Purchase #5	$7.32	6.789%	$7.817	$7.82	$7.80	$7.80
Purchase #6	$139.25	9.453%	$152.4133	$152.41	$152.40	$152.40
Purchase #7	$60.25	5.505%	$63.5668	$63.57	$63.55	$63.60
7 purchase totals =	$798.35		$868.7747	$868.78	$868.70	$868.80