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	$245.39	3.858%	$254.8571	$254.86	$254.85	$254.90
Purchase #2	$5.60	5.424%	$5.9037	$5.90	$5.90	$5.90
Purchase #3	$198.92	12.334%	$223.4548	$223.45	$223.45	$223.50
Purchase #4	$111.87	12.580%	$125.9432	$125.94	$125.95	$125.90
Purchase #5	$136.37	11.180%	$151.6162	$151.62	$151.60	$151.60
Purchase #6	$193.75	12.279%	$217.5406	$217.54	$217.55	$217.50
Purchase #7	$213.40	13.359%	$241.9081	$241.91	$241.90	$241.90
7 purchase totals =	$1,105.30		$1,221.2237	$1,221.22	$1,221.20	$1,221.20