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	$92.58	11.666%	$103.3804	$103.38	$103.40	$103.40
Purchase #2	$168.79	6.531%	$179.8137	$179.81	$179.80	$179.80
Purchase #3	$95.48	11.517%	$106.4764	$106.48	$106.50	$106.50
Purchase #4	$40.88	10.841%	$45.3118	$45.31	$45.30	$45.30
Purchase #5	$200.49	12.699%	$225.9502	$225.95	$225.95	$226.00
Purchase #6	$205.71	6.315%	$218.7006	$218.70	$218.70	$218.70
Purchase #7	$189.98	11.215%	$211.2863	$211.29	$211.30	$211.30
7 purchase totals =	$993.91		$1,090.9194	$1,090.92	$1,090.95	$1,091.00