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	$213.58	13.392%	$242.1826	$242.18	$242.20	$242.20
Purchase #2	$151.81	13.162%	$171.7912	$171.79	$171.80	$171.80
Purchase #3	$173.82	6.659%	$185.3947	$185.39	$185.40	$185.40
Purchase #4	$241.39	9.400%	$264.0807	$264.08	$264.10	$264.10
Purchase #5	$15.93	12.162%	$17.8674	$17.87	$17.85	$17.90
Purchase #6	$140.37	8.697%	$152.578	$152.58	$152.60	$152.60
Purchase #7	$41.89	4.427%	$43.7445	$43.74	$43.75	$43.70
7 purchase totals =	$978.79		$1,077.6391	$1,077.63	$1,077.70	$1,077.70