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	$98.53	7.482%	$105.902	$105.90	$105.90	$105.90
Purchase #2	$131.38	8.102%	$142.0244	$142.02	$142.00	$142.00
Purchase #3	$152.89	7.503%	$164.3613	$164.36	$164.35	$164.40
Purchase #4	$182.91	13.630%	$207.8406	$207.84	$207.85	$207.80
Purchase #5	$11.54	3.436%	$11.9365	$11.94	$11.95	$11.90
Purchase #6	$16.57	11.592%	$18.4908	$18.49	$18.50	$18.50
Purchase #7	$91.79	8.842%	$99.9061	$99.91	$99.90	$99.90
7 purchase totals =	$685.61		$750.4617	$750.46	$750.45	$750.40