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	$234.71	11.432%	$261.542	$261.54	$261.55	$261.50
Purchase #2	$178.59	4.844%	$187.2409	$187.24	$187.25	$187.20
Purchase #3	$19.26	6.785%	$20.5668	$20.57	$20.55	$20.60
Purchase #4	$158.65	4.662%	$166.0463	$166.05	$166.05	$166.00
Purchase #5	$160.84	4.441%	$167.9829	$167.98	$168.00	$168.00
Purchase #6	$18.55	10.409%	$20.4809	$20.48	$20.50	$20.50
Purchase #7	$128.61	8.190%	$139.1432	$139.14	$139.15	$139.10
7 purchase totals =	$899.21		$963.0030	$963.00	$963.05	$962.90