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	$146.80	7.181%	$157.3417	$157.34	$157.35	$157.30
Purchase #2	$229.89	9.188%	$251.0123	$251.01	$251.00	$251.00
Purchase #3	$94.64	4.225%	$98.6385	$98.64	$98.65	$98.60
Purchase #4	$68.65	13.471%	$77.8978	$77.90	$77.90	$77.90
Purchase #5	$133.56	7.490%	$143.5636	$143.56	$143.55	$143.60
Purchase #6	$192.79	11.299%	$214.5733	$214.57	$214.55	$214.60
Purchase #7	$70.33	4.562%	$73.5385	$73.54	$73.55	$73.50
7 purchase totals =	$936.66		$1,016.5657	$1,016.56	$1,016.55	$1,016.50