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	$91.44	13.160%	$103.4735	$103.47	$103.45	$103.50
Purchase #2	$199.64	13.631%	$226.8529	$226.85	$226.85	$226.90
Purchase #3	$180.34	8.696%	$196.0224	$196.02	$196.00	$196.00
Purchase #4	$40.91	11.849%	$45.7574	$45.76	$45.75	$45.80
Purchase #5	$146.68	12.337%	$164.7759	$164.78	$164.80	$164.80
Purchase #6	$125.32	7.492%	$134.709	$134.71	$134.70	$134.70
Purchase #7	$215.85	11.263%	$240.1612	$240.16	$240.15	$240.20
7 purchase totals =	$1,000.18		$1,111.7523	$1,111.75	$1,111.70	$1,111.90