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	$208.78	4.595%	$218.3734	$218.37	$218.35	$218.40
Purchase #2	$201.25	3.514%	$208.3219	$208.32	$208.30	$208.30
Purchase #3	$217.38	5.746%	$229.8707	$229.87	$229.85	$229.90
Purchase #4	$80.42	11.243%	$89.4616	$89.46	$89.45	$89.50
Purchase #5	$174.98	9.216%	$191.1062	$191.11	$191.10	$191.10
Purchase #6	$156.53	9.532%	$171.4504	$171.45	$171.45	$171.50
Purchase #7	$146.33	10.226%	$161.2937	$161.29	$161.30	$161.30
7 purchase totals =	$1,185.67		$1,269.8779	$1,269.87	$1,269.80	$1,270.00