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	$131.47	7.611%	$141.4762	$141.48	$141.50	$141.50
Purchase #2	$16.54	7.400%	$17.764	$17.76	$17.75	$17.80
Purchase #3	$186.98	12.107%	$209.6177	$209.62	$209.60	$209.60
Purchase #4	$126.47	4.248%	$131.8424	$131.84	$131.85	$131.80
Purchase #5	$157.33	7.746%	$169.5168	$169.52	$169.50	$169.50
Purchase #6	$238.50	5.207%	$250.9187	$250.92	$250.90	$250.90
Purchase #7	$144.86	12.128%	$162.4286	$162.43	$162.45	$162.40
7 purchase totals =	$1,002.15		$1,083.5644	$1,083.57	$1,083.55	$1,083.50