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	$146.76	10.719%	$162.4912	$162.49	$162.50	$162.50
Purchase #2	$55.61	11.127%	$61.7977	$61.80	$61.80	$61.80
Purchase #3	$123.31	13.329%	$139.746	$139.75	$139.75	$139.70
Purchase #4	$97.99	11.688%	$109.4431	$109.44	$109.45	$109.40
Purchase #5	$233.80	13.257%	$264.7949	$264.79	$264.80	$264.80
Purchase #6	$12.47	13.198%	$14.1158	$14.12	$14.10	$14.10
Purchase #7	$31.91	10.480%	$35.2542	$35.25	$35.25	$35.30
7 purchase totals =	$701.85		$787.6429	$787.64	$787.65	$787.60