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	$222.42	5.224%	$234.0392	$234.04	$234.05	$234.00
Purchase #2	$125.77	3.788%	$130.5342	$130.53	$130.55	$130.50
Purchase #3	$208.70	3.185%	$215.3471	$215.35	$215.35	$215.30
Purchase #4	$232.33	3.338%	$240.0852	$240.09	$240.10	$240.10
Purchase #5	$152.90	12.380%	$171.829	$171.83	$171.85	$171.80
Purchase #6	$31.41	10.803%	$34.8032	$34.80	$34.80	$34.80
Purchase #7	$131.47	7.842%	$141.7799	$141.78	$141.80	$141.80
7 purchase totals =	$1,105.00		$1,168.4178	$1,168.42	$1,168.50	$1,168.30