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	$234.37	4.510%	$244.9401	$244.94	$244.95	$244.90
Purchase #2	$245.41	3.234%	$253.3466	$253.35	$253.35	$253.30
Purchase #3	$42.77	5.491%	$45.1185	$45.12	$45.10	$45.10
Purchase #4	$49.55	6.102%	$52.5735	$52.57	$52.55	$52.60
Purchase #5	$249.66	13.212%	$282.6451	$282.65	$282.65	$282.60
Purchase #6	$66.76	5.837%	$70.6568	$70.66	$70.65	$70.70
Purchase #7	$51.90	7.644%	$55.8672	$55.87	$55.85	$55.90
7 purchase totals =	$940.42		$1,005.1478	$1,005.16	$1,005.10	$1,005.10