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	$140.61	8.669%	$152.7995	$152.80	$152.80	$152.80
Purchase #2	$74.88	8.812%	$81.4784	$81.48	$81.50	$81.50
Purchase #3	$181.90	7.803%	$196.0937	$196.09	$196.10	$196.10
Purchase #4	$39.34	4.598%	$41.1489	$41.15	$41.15	$41.10
Purchase #5	$133.72	13.626%	$151.9407	$151.94	$151.95	$151.90
Purchase #6	$234.78	3.836%	$243.7862	$243.79	$243.80	$243.80
Purchase #7	$12.91	10.383%	$14.2504	$14.25	$14.25	$14.30
7 purchase totals =	$818.14		$881.4978	$881.50	$881.55	$881.50