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	$121.76	9.436%	$133.2493	$133.25	$133.25	$133.20
Purchase #2	$102.72	6.668%	$109.5694	$109.57	$109.55	$109.60
Purchase #3	$45.87	12.151%	$51.4437	$51.44	$51.45	$51.40
Purchase #4	$108.27	9.247%	$118.2817	$118.28	$118.30	$118.30
Purchase #5	$196.55	13.291%	$222.6735	$222.67	$222.65	$222.70
Purchase #6	$121.91	4.394%	$127.2667	$127.27	$127.25	$127.30
Purchase #7	$218.53	7.862%	$235.7108	$235.71	$235.70	$235.70
7 purchase totals =	$915.61		$998.1951	$998.19	$998.15	$998.20