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	$200.45	4.395%	$209.2598	$209.26	$209.25	$209.30
Purchase #2	$28.30	11.466%	$31.5449	$31.54	$31.55	$31.50
Purchase #3	$151.64	6.822%	$161.9849	$161.98	$162.00	$162.00
Purchase #4	$241.91	11.366%	$269.4055	$269.41	$269.40	$269.40
Purchase #5	$187.49	7.125%	$200.8487	$200.85	$200.85	$200.80
Purchase #6	$57.30	3.428%	$59.2642	$59.26	$59.25	$59.30
Purchase #7	$140.88	11.375%	$156.9051	$156.91	$156.90	$156.90
7 purchase totals =	$1,007.97		$1,089.2131	$1,089.21	$1,089.20	$1,089.20