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	$57.59	3.452%	$59.578	$59.58	$59.60	$59.60
Purchase #2	$81.86	12.404%	$92.0139	$92.01	$92.00	$92.00
Purchase #3	$49.37	11.118%	$54.859	$54.86	$54.85	$54.90
Purchase #4	$192.91	6.770%	$205.97	$205.97	$205.95	$206.00
Purchase #5	$93.97	6.356%	$99.9427	$99.94	$99.95	$99.90
Purchase #6	$150.38	13.808%	$171.1445	$171.14	$171.15	$171.10
Purchase #7	$231.76	8.690%	$251.8999	$251.90	$251.90	$251.90
7 purchase totals =	$857.84		$935.4080	$935.40	$935.40	$935.40