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	$79.88	12.472%	$89.8426	$89.84	$89.85	$89.80
Purchase #2	$101.84	10.661%	$112.6972	$112.70	$112.70	$112.70
Purchase #3	$83.89	7.531%	$90.2078	$90.21	$90.20	$90.20
Purchase #4	$201.88	7.205%	$216.4255	$216.43	$216.45	$216.40
Purchase #5	$182.65	9.487%	$199.978	$199.98	$200.00	$200.00
Purchase #6	$42.98	9.726%	$47.1602	$47.16	$47.15	$47.20
Purchase #7	$218.37	12.334%	$245.3038	$245.30	$245.30	$245.30
7 purchase totals =	$911.49		$1,001.6151	$1,001.62	$1,001.65	$1,001.60