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	$171.36	6.114%	$181.837	$181.84	$181.85	$181.80
Purchase #2	$78.86	8.570%	$85.6183	$85.62	$85.60	$85.60
Purchase #3	$178.57	7.195%	$191.4181	$191.42	$191.40	$191.40
Purchase #4	$84.88	12.867%	$95.8015	$95.80	$95.80	$95.80
Purchase #5	$181.66	10.314%	$200.3964	$200.40	$200.40	$200.40
Purchase #6	$147.87	9.562%	$162.0093	$162.01	$162.00	$162.00
Purchase #7	$171.25	10.722%	$189.6114	$189.61	$189.60	$189.60
7 purchase totals =	$1,014.45		$1,106.6920	$1,106.70	$1,106.65	$1,106.60