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	$43.82	3.533%	$45.3682	$45.37	$45.35	$45.40
Purchase #2	$168.63	9.173%	$184.0984	$184.10	$184.10	$184.10
Purchase #3	$134.48	7.533%	$144.6104	$144.61	$144.60	$144.60
Purchase #4	$149.92	10.176%	$165.1759	$165.18	$165.20	$165.20
Purchase #5	$71.73	9.872%	$78.8112	$78.81	$78.80	$78.80
Purchase #6	$235.44	13.698%	$267.6906	$267.69	$267.70	$267.70
Purchase #7	$198.59	7.712%	$213.9053	$213.91	$213.90	$213.90
7 purchase totals =	$1,002.61		$1,099.6600	$1,099.67	$1,099.65	$1,099.70