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	$81.85	12.423%	$92.0182	$92.02	$92.00	$92.00
Purchase #2	$113.25	12.469%	$127.3711	$127.37	$127.35	$127.40
Purchase #3	$101.98	4.781%	$106.8557	$106.86	$106.85	$106.90
Purchase #4	$83.80	7.278%	$89.899	$89.90	$89.90	$89.90
Purchase #5	$49.61	9.851%	$54.4971	$54.50	$54.50	$54.50
Purchase #6	$191.57	5.120%	$201.3784	$201.38	$201.40	$201.40
Purchase #7	$118.53	9.260%	$129.5059	$129.51	$129.50	$129.50
7 purchase totals =	$740.59		$801.5254	$801.54	$801.50	$801.60