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	$130.96	10.796%	$145.0984	$145.10	$145.10	$145.10
Purchase #2	$31.83	7.224%	$34.1294	$34.13	$34.15	$34.10
Purchase #3	$81.62	10.108%	$89.8701	$89.87	$89.85	$89.90
Purchase #4	$86.67	11.107%	$96.2964	$96.30	$96.30	$96.30
Purchase #5	$76.26	5.161%	$80.1958	$80.20	$80.20	$80.20
Purchase #6	$22.90	6.819%	$24.4616	$24.46	$24.45	$24.50
Purchase #7	$94.42	9.781%	$103.6552	$103.66	$103.65	$103.70
7 purchase totals =	$524.66		$573.7069	$573.72	$573.70	$573.80