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	$237.95	13.270%	$269.526	$269.53	$269.55	$269.50
Purchase #2	$86.61	3.649%	$89.7704	$89.77	$89.75	$89.80
Purchase #3	$88.98	7.350%	$95.52	$95.52	$95.50	$95.50
Purchase #4	$187.25	4.198%	$195.1108	$195.11	$195.10	$195.10
Purchase #5	$9.79	12.196%	$10.984	$10.98	$11.00	$11.00
Purchase #6	$210.96	4.826%	$221.1409	$221.14	$221.15	$221.10
Purchase #7	$203.38	4.122%	$211.7633	$211.76	$211.75	$211.80
7 purchase totals =	$1,024.92		$1,093.8154	$1,093.81	$1,093.80	$1,093.80