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	$180.78	5.582%	$190.8711	$190.87	$190.85	$190.90
Purchase #2	$101.48	3.801%	$105.3373	$105.34	$105.35	$105.30
Purchase #3	$213.71	4.439%	$223.1966	$223.20	$223.20	$223.20
Purchase #4	$36.42	7.560%	$39.1734	$39.17	$39.15	$39.20
Purchase #5	$41.98	8.477%	$45.5386	$45.54	$45.55	$45.50
Purchase #6	$95.27	8.818%	$103.6709	$103.67	$103.65	$103.70
Purchase #7	$94.52	7.243%	$101.3661	$101.37	$101.35	$101.40
7 purchase totals =	$764.16		$809.1540	$809.16	$809.10	$809.20