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	$167.98	4.562%	$175.6432	$175.64	$175.65	$175.60
Purchase #2	$145.37	7.642%	$156.4792	$156.48	$156.50	$156.50
Purchase #3	$206.81	3.401%	$213.8436	$213.84	$213.85	$213.80
Purchase #4	$79.59	7.102%	$85.2425	$85.24	$85.25	$85.20
Purchase #5	$35.67	12.522%	$40.1366	$40.14	$40.15	$40.10
Purchase #6	$15.57	8.587%	$16.907	$16.91	$16.90	$16.90
Purchase #7	$25.83	6.599%	$27.5345	$27.53	$27.55	$27.50
7 purchase totals =	$676.82		$715.7866	$715.78	$715.85	$715.60