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	$204.67	5.421%	$215.7652	$215.77	$215.75	$215.80
Purchase #2	$86.42	6.343%	$91.9016	$91.90	$91.90	$91.90
Purchase #3	$39.77	6.366%	$42.3018	$42.30	$42.30	$42.30
Purchase #4	$219.50	4.837%	$230.1172	$230.12	$230.10	$230.10
Purchase #5	$218.98	4.243%	$228.2713	$228.27	$228.25	$228.30
Purchase #6	$220.64	11.741%	$246.5453	$246.55	$246.55	$246.50
Purchase #7	$12.75	9.187%	$13.9213	$13.92	$13.90	$13.90
7 purchase totals =	$1,002.73		$1,068.8237	$1,068.83	$1,068.75	$1,068.80