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	$165.38	8.193%	$178.9296	$178.93	$178.95	$178.90
Purchase #2	$247.32	6.874%	$264.3208	$264.32	$264.30	$264.30
Purchase #3	$102.33	10.841%	$113.4236	$113.42	$113.40	$113.40
Purchase #4	$14.46	3.602%	$14.9808	$14.98	$15.00	$15.00
Purchase #5	$123.95	3.315%	$128.0589	$128.06	$128.05	$128.10
Purchase #6	$93.48	13.304%	$105.9166	$105.92	$105.90	$105.90
Purchase #7	$139.84	7.860%	$150.8314	$150.83	$150.85	$150.80
7 purchase totals =	$886.76		$956.4617	$956.46	$956.45	$956.40