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	$117.95	6.674%	$125.822	$125.82	$125.80	$125.80
Purchase #2	$49.44	9.296%	$54.0359	$54.04	$54.05	$54.00
Purchase #3	$46.78	10.736%	$51.8023	$51.80	$51.80	$51.80
Purchase #4	$159.40	7.601%	$171.516	$171.52	$171.50	$171.50
Purchase #5	$95.39	6.582%	$101.6686	$101.67	$101.65	$101.70
Purchase #6	$40.41	13.279%	$45.776	$45.78	$45.80	$45.80
Purchase #7	$103.96	11.124%	$115.5245	$115.52	$115.50	$115.50
7 purchase totals =	$613.33		$666.1453	$666.15	$666.10	$666.10