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	$181.66	7.668%	$195.5897	$195.59	$195.60	$195.60
Purchase #2	$175.74	8.601%	$190.8554	$190.86	$190.85	$190.90
Purchase #3	$78.72	3.228%	$81.2611	$81.26	$81.25	$81.30
Purchase #4	$161.77	11.586%	$180.5127	$180.51	$180.50	$180.50
Purchase #5	$98.29	4.803%	$103.0109	$103.01	$103.00	$103.00
Purchase #6	$11.38	6.223%	$12.0882	$12.09	$12.10	$12.10
Purchase #7	$203.59	5.608%	$215.0073	$215.01	$215.00	$215.00
7 purchase totals =	$911.15		$978.3253	$978.33	$978.30	$978.40