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	$137.46	5.260%	$144.6904	$144.69	$144.70	$144.70
Purchase #2	$231.72	13.735%	$263.5467	$263.55	$263.55	$263.50
Purchase #3	$46.82	3.588%	$48.4999	$48.50	$48.50	$48.50
Purchase #4	$245.97	9.182%	$268.555	$268.56	$268.55	$268.60
Purchase #5	$52.65	7.327%	$56.5077	$56.51	$56.50	$56.50
Purchase #6	$111.72	10.399%	$123.3378	$123.34	$123.35	$123.30
Purchase #7	$128.44	10.516%	$141.9468	$141.95	$141.95	$141.90
7 purchase totals =	$954.78		$1,047.0843	$1,047.10	$1,047.10	$1,047.00