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	$160.75	11.520%	$179.2684	$179.27	$179.25	$179.30
Purchase #2	$196.27	11.222%	$218.2954	$218.30	$218.30	$218.30
Purchase #3	$31.91	6.861%	$34.0993	$34.10	$34.10	$34.10
Purchase #4	$186.28	5.517%	$196.5571	$196.56	$196.55	$196.60
Purchase #5	$117.33	11.706%	$131.0646	$131.06	$131.05	$131.10
Purchase #6	$91.42	11.873%	$102.2743	$102.27	$102.25	$102.30
Purchase #7	$228.31	12.533%	$256.9241	$256.92	$256.90	$256.90
7 purchase totals =	$1,012.27		$1,118.4832	$1,118.48	$1,118.40	$1,118.60