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	$89.36	11.630%	$99.7526	$99.75	$99.75	$99.80
Purchase #2	$104.48	4.750%	$109.4428	$109.44	$109.45	$109.40
Purchase #3	$53.40	6.584%	$56.9159	$56.92	$56.90	$56.90
Purchase #4	$230.26	11.533%	$256.8159	$256.82	$256.80	$256.80
Purchase #5	$248.83	11.177%	$276.6417	$276.64	$276.65	$276.60
Purchase #6	$24.74	10.700%	$27.3872	$27.39	$27.40	$27.40
Purchase #7	$135.78	8.632%	$147.5005	$147.50	$147.50	$147.50
7 purchase totals =	$886.85		$974.4566	$974.46	$974.45	$974.40