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	$222.32	4.550%	$232.4356	$232.44	$232.45	$232.40
Purchase #2	$42.31	7.702%	$45.5687	$45.57	$45.55	$45.60
Purchase #3	$200.47	4.850%	$210.1928	$210.19	$210.20	$210.20
Purchase #4	$67.44	5.176%	$70.9307	$70.93	$70.95	$70.90
Purchase #5	$58.85	4.108%	$61.2676	$61.27	$61.25	$61.30
Purchase #6	$222.42	6.455%	$236.7772	$236.78	$236.80	$236.80
Purchase #7	$127.39	12.623%	$143.4704	$143.47	$143.45	$143.50
7 purchase totals =	$941.20		$1,000.6430	$1,000.65	$1,000.65	$1,000.70