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	$114.32	4.847%	$119.8611	$119.86	$119.85	$119.90
Purchase #2	$88.93	12.219%	$99.7964	$99.80	$99.80	$99.80
Purchase #3	$68.43	12.267%	$76.8243	$76.82	$76.80	$76.80
Purchase #4	$30.50	11.402%	$33.9776	$33.98	$34.00	$34.00
Purchase #5	$79.31	5.796%	$83.9068	$83.91	$83.90	$83.90
Purchase #6	$137.39	5.334%	$144.7184	$144.72	$144.70	$144.70
Purchase #7	$186.58	5.307%	$196.4818	$196.48	$196.50	$196.50
7 purchase totals =	$705.46		$755.5664	$755.57	$755.55	$755.60