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	$75.38	8.220%	$81.5762	$81.58	$81.60	$81.60
Purchase #2	$21.47	5.769%	$22.7086	$22.71	$22.70	$22.70
Purchase #3	$136.71	6.498%	$145.5934	$145.59	$145.60	$145.60
Purchase #4	$186.89	7.342%	$200.6115	$200.61	$200.60	$200.60
Purchase #5	$223.90	4.314%	$233.559	$233.56	$233.55	$233.60
Purchase #6	$183.56	11.649%	$204.9429	$204.94	$204.95	$204.90
Purchase #7	$21.43	5.397%	$22.5866	$22.59	$22.60	$22.60
7 purchase totals =	$849.34		$911.5782	$911.58	$911.60	$911.60