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	$70.55	11.548%	$78.6971	$78.70	$78.70	$78.70
Purchase #2	$233.87	13.479%	$265.3933	$265.39	$265.40	$265.40
Purchase #3	$119.82	6.621%	$127.7533	$127.75	$127.75	$127.80
Purchase #4	$93.40	4.297%	$97.4134	$97.41	$97.40	$97.40
Purchase #5	$221.92	10.645%	$245.5434	$245.54	$245.55	$245.50
Purchase #6	$172.28	7.730%	$185.5972	$185.60	$185.60	$185.60
Purchase #7	$41.74	6.704%	$44.5382	$44.54	$44.55	$44.50
7 purchase totals =	$953.58		$1,044.9359	$1,044.93	$1,044.95	$1,044.90