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	$76.91	9.291%	$84.0557	$84.06	$84.05	$84.10
Purchase #2	$102.43	11.524%	$114.234	$114.23	$114.25	$114.20
Purchase #3	$212.28	13.646%	$241.2477	$241.25	$241.25	$241.20
Purchase #4	$246.50	3.559%	$255.2729	$255.27	$255.25	$255.30
Purchase #5	$61.98	11.748%	$69.2614	$69.26	$69.25	$69.30
Purchase #6	$178.32	10.428%	$196.9152	$196.92	$196.90	$196.90
Purchase #7	$93.25	11.143%	$103.6408	$103.64	$103.65	$103.60
7 purchase totals =	$971.67		$1,064.6277	$1,064.63	$1,064.60	$1,064.60