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	$32.53	13.345%	$36.8711	$36.87	$36.85	$36.90
Purchase #2	$147.73	13.735%	$168.0207	$168.02	$168.00	$168.00
Purchase #3	$65.53	11.196%	$72.8667	$72.87	$72.85	$72.90
Purchase #4	$226.51	10.524%	$250.3479	$250.35	$250.35	$250.30
Purchase #5	$162.73	10.856%	$180.396	$180.40	$180.40	$180.40
Purchase #6	$122.62	7.731%	$132.0998	$132.10	$132.10	$132.10
Purchase #7	$33.55	10.804%	$37.1747	$37.17	$37.15	$37.20
7 purchase totals =	$791.20		$877.7769	$877.78	$877.70	$877.80