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	$38.83	10.526%	$42.9172	$42.92	$42.90	$42.90
Purchase #2	$169.40	6.448%	$180.3229	$180.32	$180.30	$180.30
Purchase #3	$203.59	5.124%	$214.022	$214.02	$214.00	$214.00
Purchase #4	$143.75	11.857%	$160.7944	$160.79	$160.80	$160.80
Purchase #5	$43.88	4.406%	$45.8134	$45.81	$45.80	$45.80
Purchase #6	$241.52	3.595%	$250.2026	$250.20	$250.20	$250.20
Purchase #7	$158.98	9.787%	$174.5394	$174.54	$174.55	$174.50
7 purchase totals =	$999.95		$1,068.6119	$1,068.60	$1,068.55	$1,068.50