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	$33.59	8.562%	$36.466	$36.47	$36.45	$36.50
Purchase #2	$45.37	3.859%	$47.1208	$47.12	$47.10	$47.10
Purchase #3	$233.27	8.299%	$252.6291	$252.63	$252.65	$252.60
Purchase #4	$63.79	13.148%	$72.1771	$72.18	$72.20	$72.20
Purchase #5	$79.90	4.852%	$83.7767	$83.78	$83.80	$83.80
Purchase #6	$108.87	13.307%	$123.3573	$123.36	$123.35	$123.40
Purchase #7	$82.84	8.427%	$89.8209	$89.82	$89.80	$89.80
7 purchase totals =	$647.63		$705.3479	$705.36	$705.35	$705.40