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	$76.56	11.381%	$85.2733	$85.27	$85.25	$85.30
Purchase #2	$214.54	7.169%	$229.9204	$229.92	$229.90	$229.90
Purchase #3	$29.86	12.216%	$33.5077	$33.51	$33.50	$33.50
Purchase #4	$95.39	12.155%	$106.9847	$106.98	$107.00	$107.00
Purchase #5	$100.41	13.846%	$114.3128	$114.31	$114.30	$114.30
Purchase #6	$218.54	11.102%	$242.8023	$242.80	$242.80	$242.80
Purchase #7	$73.77	12.280%	$82.829	$82.83	$82.85	$82.80
7 purchase totals =	$809.07		$895.6302	$895.62	$895.60	$895.60