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	$97.58	8.466%	$105.8411	$105.84	$105.85	$105.80
Purchase #2	$126.83	12.230%	$142.3413	$142.34	$142.35	$142.30
Purchase #3	$223.82	4.512%	$233.9188	$233.92	$233.90	$233.90
Purchase #4	$207.54	7.164%	$222.4082	$222.41	$222.40	$222.40
Purchase #5	$169.67	3.172%	$175.0519	$175.05	$175.05	$175.10
Purchase #6	$7.47	8.784%	$8.1262	$8.13	$8.15	$8.10
Purchase #7	$137.63	3.131%	$141.9392	$141.94	$141.95	$141.90
7 purchase totals =	$970.54		$1,029.6267	$1,029.63	$1,029.65	$1,029.50