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	$198.35	12.861%	$223.8598	$223.86	$223.85	$223.90
Purchase #2	$47.84	8.280%	$51.8012	$51.80	$51.80	$51.80
Purchase #3	$77.75	5.624%	$82.1227	$82.12	$82.10	$82.10
Purchase #4	$78.48	12.543%	$88.3237	$88.32	$88.30	$88.30
Purchase #5	$122.43	7.509%	$131.6233	$131.62	$131.60	$131.60
Purchase #6	$39.26	13.459%	$44.544	$44.54	$44.55	$44.50
Purchase #7	$141.46	6.415%	$150.5347	$150.53	$150.55	$150.50
7 purchase totals =	$705.57		$772.8094	$772.79	$772.75	$772.70