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	$61.62	13.395%	$69.874	$69.87	$69.85	$69.90
Purchase #2	$199.76	9.215%	$218.1679	$218.17	$218.15	$218.20
Purchase #3	$249.57	7.765%	$268.9491	$268.95	$268.95	$268.90
Purchase #4	$205.98	9.794%	$226.1537	$226.15	$226.15	$226.20
Purchase #5	$225.34	7.497%	$242.2337	$242.23	$242.25	$242.20
Purchase #6	$89.51	11.481%	$99.7866	$99.79	$99.80	$99.80
Purchase #7	$63.36	12.659%	$71.3807	$71.38	$71.40	$71.40
7 purchase totals =	$1,095.14		$1,196.5457	$1,196.54	$1,196.55	$1,196.60