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	$151.40	3.188%	$156.2266	$156.23	$156.25	$156.20
Purchase #2	$198.52	7.202%	$212.8174	$212.82	$212.80	$212.80
Purchase #3	$41.91	4.836%	$43.9368	$43.94	$43.95	$43.90
Purchase #4	$120.93	6.111%	$128.32	$128.32	$128.30	$128.30
Purchase #5	$190.79	11.756%	$213.2193	$213.22	$213.20	$213.20
Purchase #6	$240.53	4.322%	$250.9257	$250.93	$250.95	$250.90
Purchase #7	$145.83	5.555%	$153.9309	$153.93	$153.95	$153.90
7 purchase totals =	$1,089.91		$1,159.3767	$1,159.39	$1,159.40	$1,159.20