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	$223.31	3.709%	$231.5926	$231.59	$231.60	$231.60
Purchase #2	$35.42	5.516%	$37.3738	$37.37	$37.35	$37.40
Purchase #3	$187.58	5.595%	$198.0751	$198.08	$198.10	$198.10
Purchase #4	$248.88	8.168%	$269.2085	$269.21	$269.20	$269.20
Purchase #5	$110.30	7.363%	$118.4214	$118.42	$118.40	$118.40
Purchase #6	$48.88	5.281%	$51.4614	$51.46	$51.45	$51.50
Purchase #7	$102.54	6.619%	$109.3271	$109.33	$109.35	$109.30
7 purchase totals =	$956.91		$1,015.4599	$1,015.46	$1,015.45	$1,015.50