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	$205.82	3.740%	$213.5177	$213.52	$213.50	$213.50
Purchase #2	$40.73	7.820%	$43.9151	$43.92	$43.90	$43.90
Purchase #3	$90.26	13.654%	$102.5841	$102.58	$102.60	$102.60
Purchase #4	$30.92	10.828%	$34.268	$34.27	$34.25	$34.30
Purchase #5	$194.82	11.151%	$216.5444	$216.54	$216.55	$216.50
Purchase #6	$243.44	8.591%	$264.3539	$264.35	$264.35	$264.40
Purchase #7	$51.94	7.711%	$55.9451	$55.95	$55.95	$55.90
7 purchase totals =	$857.93		$931.1283	$931.13	$931.10	$931.10