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	$158.43	3.754%	$164.3775	$164.38	$164.40	$164.40
Purchase #2	$63.40	12.836%	$71.538	$71.54	$71.55	$71.50
Purchase #3	$96.97	5.710%	$102.507	$102.51	$102.50	$102.50
Purchase #4	$242.45	8.486%	$263.0243	$263.02	$263.00	$263.00
Purchase #5	$22.46	13.373%	$25.4636	$25.46	$25.45	$25.50
Purchase #6	$152.40	11.690%	$170.2156	$170.22	$170.20	$170.20
Purchase #7	$125.32	11.592%	$139.8471	$139.85	$139.85	$139.80
7 purchase totals =	$861.43		$936.9731	$936.98	$936.95	$936.90