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	$223.50	10.654%	$247.3117	$247.31	$247.30	$247.30
Purchase #2	$89.99	12.314%	$101.0714	$101.07	$101.05	$101.10
Purchase #3	$229.86	6.714%	$245.2928	$245.29	$245.30	$245.30
Purchase #4	$42.82	6.384%	$45.5536	$45.55	$45.55	$45.60
Purchase #5	$72.98	9.746%	$80.0926	$80.09	$80.10	$80.10
Purchase #6	$139.59	3.498%	$144.4729	$144.47	$144.45	$144.50
Purchase #7	$197.27	5.680%	$208.4749	$208.47	$208.45	$208.50
7 purchase totals =	$996.01		$1,072.2699	$1,072.25	$1,072.20	$1,072.40