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	$126.61	13.682%	$143.9328	$143.93	$143.95	$143.90
Purchase #2	$165.87	3.129%	$171.0601	$171.06	$171.05	$171.10
Purchase #3	$36.72	5.291%	$38.6629	$38.66	$38.65	$38.70
Purchase #4	$84.95	13.679%	$96.5703	$96.57	$96.55	$96.60
Purchase #5	$128.92	12.427%	$144.9409	$144.94	$144.95	$144.90
Purchase #6	$53.49	10.435%	$59.0717	$59.07	$59.05	$59.10
Purchase #7	$72.51	13.254%	$82.1205	$82.12	$82.10	$82.10
7 purchase totals =	$669.07		$736.3592	$736.35	$736.30	$736.40