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	$162.52	3.661%	$168.4699	$168.47	$168.45	$168.50
Purchase #2	$106.40	10.182%	$117.2336	$117.23	$117.25	$117.20
Purchase #3	$117.81	11.390%	$131.2286	$131.23	$131.25	$131.20
Purchase #4	$48.96	6.495%	$52.14	$52.14	$52.15	$52.10
Purchase #5	$219.77	6.777%	$234.6638	$234.66	$234.65	$234.70
Purchase #6	$48.87	11.642%	$54.5594	$54.56	$54.55	$54.60
Purchase #7	$36.83	6.475%	$39.2147	$39.21	$39.20	$39.20
7 purchase totals =	$741.16		$797.5100	$797.50	$797.50	$797.50