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	$109.62	13.814%	$124.7629	$124.76	$124.75	$124.80
Purchase #2	$180.29	11.318%	$200.6952	$200.70	$200.70	$200.70
Purchase #3	$219.61	5.566%	$231.8335	$231.83	$231.85	$231.80
Purchase #4	$51.35	6.455%	$54.6646	$54.66	$54.65	$54.70
Purchase #5	$242.59	9.387%	$265.3619	$265.36	$265.35	$265.40
Purchase #6	$22.92	10.483%	$25.3227	$25.32	$25.30	$25.30
Purchase #7	$234.60	3.113%	$241.9031	$241.90	$241.90	$241.90
7 purchase totals =	$1,060.98		$1,144.5439	$1,144.53	$1,144.50	$1,144.60