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	$182.52	7.503%	$196.2145	$196.21	$196.20	$196.20
Purchase #2	$103.53	10.473%	$114.3727	$114.37	$114.35	$114.40
Purchase #3	$11.35	7.539%	$12.2057	$12.21	$12.20	$12.20
Purchase #4	$213.44	9.340%	$233.3753	$233.38	$233.40	$233.40
Purchase #5	$33.25	5.654%	$35.13	$35.13	$35.15	$35.10
Purchase #6	$217.76	11.728%	$243.2989	$243.30	$243.30	$243.30
Purchase #7	$156.75	3.443%	$162.1469	$162.15	$162.15	$162.10
7 purchase totals =	$918.60		$996.7440	$996.75	$996.75	$996.70