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	$89.83	7.861%	$96.8915	$96.89	$96.90	$96.90
Purchase #2	$176.90	8.601%	$192.1152	$192.12	$192.10	$192.10
Purchase #3	$53.52	11.280%	$59.5571	$59.56	$59.55	$59.60
Purchase #4	$132.37	7.689%	$142.5479	$142.55	$142.55	$142.50
Purchase #5	$248.37	9.103%	$270.9791	$270.98	$271.00	$271.00
Purchase #6	$64.33	3.608%	$66.651	$66.65	$66.65	$66.70
Purchase #7	$221.69	9.591%	$242.9523	$242.95	$242.95	$243.00
7 purchase totals =	$987.01		$1,071.6941	$1,071.70	$1,071.70	$1,071.80