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	$94.80	5.793%	$100.2918	$100.29	$100.30	$100.30
Purchase #2	$67.41	5.144%	$70.8776	$70.88	$70.90	$70.90
Purchase #3	$100.30	13.404%	$113.7442	$113.74	$113.75	$113.70
Purchase #4	$132.90	3.738%	$137.8678	$137.87	$137.85	$137.90
Purchase #5	$193.35	3.715%	$200.533	$200.53	$200.55	$200.50
Purchase #6	$181.31	10.379%	$200.1282	$200.13	$200.15	$200.10
Purchase #7	$25.56	11.231%	$28.4306	$28.43	$28.45	$28.40
7 purchase totals =	$795.63		$851.8732	$851.87	$851.95	$851.80