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	$98.42	3.345%	$101.7121	$101.71	$101.70	$101.70
Purchase #2	$127.45	3.534%	$131.9541	$131.95	$131.95	$132.00
Purchase #3	$121.36	4.731%	$127.1015	$127.10	$127.10	$127.10
Purchase #4	$152.97	9.558%	$167.5909	$167.59	$167.60	$167.60
Purchase #5	$29.82	8.701%	$32.4146	$32.41	$32.40	$32.40
Purchase #6	$68.70	3.565%	$71.1492	$71.15	$71.15	$71.10
Purchase #7	$209.64	11.241%	$233.2056	$233.21	$233.20	$233.20
7 purchase totals =	$808.36		$865.1280	$865.12	$865.10	$865.10