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	$235.45	9.331%	$257.4198	$257.42	$257.40	$257.40
Purchase #2	$92.68	9.475%	$101.4614	$101.46	$101.45	$101.50
Purchase #3	$230.33	11.518%	$256.8594	$256.86	$256.85	$256.90
Purchase #4	$234.59	3.152%	$241.9843	$241.98	$242.00	$242.00
Purchase #5	$51.94	6.836%	$55.4906	$55.49	$55.50	$55.50
Purchase #6	$133.36	11.236%	$148.3443	$148.34	$148.35	$148.30
Purchase #7	$109.69	13.119%	$124.0802	$124.08	$124.10	$124.10
7 purchase totals =	$1,088.04		$1,185.6400	$1,185.63	$1,185.65	$1,185.70