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	$181.61	5.135%	$190.9357	$190.94	$190.95	$190.90
Purchase #2	$149.76	12.129%	$167.9244	$167.92	$167.90	$167.90
Purchase #3	$182.52	3.636%	$189.1564	$189.16	$189.15	$189.20
Purchase #4	$31.52	12.660%	$35.5104	$35.51	$35.50	$35.50
Purchase #5	$246.53	4.258%	$257.0272	$257.03	$257.05	$257.00
Purchase #6	$92.52	3.640%	$95.8877	$95.89	$95.90	$95.90
Purchase #7	$72.89	4.732%	$76.3392	$76.34	$76.35	$76.30
7 purchase totals =	$957.35		$1,012.7810	$1,012.79	$1,012.80	$1,012.70