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	$95.32	9.354%	$104.2362	$104.24	$104.25	$104.20
Purchase #2	$79.69	7.752%	$85.8676	$85.87	$85.85	$85.90
Purchase #3	$88.49	7.642%	$95.2524	$95.25	$95.25	$95.30
Purchase #4	$65.90	9.455%	$72.1308	$72.13	$72.15	$72.10
Purchase #5	$241.73	9.188%	$263.9402	$263.94	$263.95	$263.90
Purchase #6	$91.85	6.833%	$98.1261	$98.13	$98.15	$98.10
Purchase #7	$124.63	5.625%	$131.6404	$131.64	$131.65	$131.60
7 purchase totals =	$787.61		$851.1937	$851.20	$851.25	$851.10