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	$82.36	12.165%	$92.3791	$92.38	$92.40	$92.40
Purchase #2	$207.25	8.312%	$224.4766	$224.48	$224.50	$224.50
Purchase #3	$210.81	7.261%	$226.1169	$226.12	$226.10	$226.10
Purchase #4	$133.48	4.616%	$139.6414	$139.64	$139.65	$139.60
Purchase #5	$72.47	8.132%	$78.3633	$78.36	$78.35	$78.40
Purchase #6	$245.83	6.164%	$260.983	$260.98	$261.00	$261.00
Purchase #7	$152.33	10.224%	$167.9042	$167.90	$167.90	$167.90
7 purchase totals =	$1,104.53		$1,189.8645	$1,189.86	$1,189.90	$1,189.90