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	$119.93	9.437%	$131.2478	$131.25	$131.25	$131.20
Purchase #2	$127.34	10.778%	$141.0647	$141.06	$141.05	$141.10
Purchase #3	$35.79	4.464%	$37.3877	$37.39	$37.40	$37.40
Purchase #4	$135.66	7.731%	$146.1479	$146.15	$146.15	$146.10
Purchase #5	$133.27	7.543%	$143.3226	$143.32	$143.30	$143.30
Purchase #6	$194.92	4.693%	$204.0676	$204.07	$204.05	$204.10
Purchase #7	$244.45	5.402%	$257.6552	$257.66	$257.65	$257.70
7 purchase totals =	$991.36		$1,060.8935	$1,060.90	$1,060.85	$1,060.90