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	$157.54	7.710%	$169.6863	$169.69	$169.70	$169.70
Purchase #2	$106.25	9.613%	$116.4638	$116.46	$116.45	$116.50
Purchase #3	$83.48	3.204%	$86.1547	$86.15	$86.15	$86.20
Purchase #4	$59.94	13.300%	$67.912	$67.91	$67.90	$67.90
Purchase #5	$82.71	6.823%	$88.3533	$88.35	$88.35	$88.40
Purchase #6	$162.35	5.857%	$171.8588	$171.86	$171.85	$171.90
Purchase #7	$142.81	4.108%	$148.6766	$148.68	$148.70	$148.70
7 purchase totals =	$795.08		$849.1055	$849.10	$849.10	$849.30