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	$143.71	8.868%	$156.4542	$156.45	$156.45	$156.50
Purchase #2	$222.72	5.214%	$234.3326	$234.33	$234.35	$234.30
Purchase #3	$6.86	6.229%	$7.2873	$7.29	$7.30	$7.30
Purchase #4	$92.48	7.721%	$99.6204	$99.62	$99.60	$99.60
Purchase #5	$21.76	8.498%	$23.6092	$23.61	$23.60	$23.60
Purchase #6	$18.33	10.841%	$20.3172	$20.32	$20.30	$20.30
Purchase #7	$228.82	12.276%	$256.9099	$256.91	$256.90	$256.90
7 purchase totals =	$734.68		$798.5308	$798.53	$798.50	$798.50