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	$44.61	9.326%	$48.7703	$48.77	$48.75	$48.80
Purchase #2	$27.89	11.674%	$31.1459	$31.15	$31.15	$31.10
Purchase #3	$208.35	8.557%	$226.1785	$226.18	$226.20	$226.20
Purchase #4	$86.34	4.207%	$89.9723	$89.97	$89.95	$90.00
Purchase #5	$153.25	7.451%	$164.6687	$164.67	$164.65	$164.70
Purchase #6	$198.77	8.436%	$215.5382	$215.54	$215.55	$215.50
Purchase #7	$250.97	9.816%	$275.6052	$275.61	$275.60	$275.60
7 purchase totals =	$970.18		$1,051.8791	$1,051.89	$1,051.85	$1,051.90