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	$185.56	5.680%	$196.0998	$196.10	$196.10	$196.10
Purchase #2	$134.77	9.405%	$147.4451	$147.45	$147.45	$147.40
Purchase #3	$135.54	5.444%	$142.9188	$142.92	$142.90	$142.90
Purchase #4	$231.37	7.210%	$248.0518	$248.05	$248.05	$248.10
Purchase #5	$177.30	12.654%	$199.7355	$199.74	$199.75	$199.70
Purchase #6	$30.92	8.280%	$33.4802	$33.48	$33.50	$33.50
Purchase #7	$190.85	4.606%	$199.6406	$199.64	$199.65	$199.60
7 purchase totals =	$1,086.31		$1,167.3718	$1,167.38	$1,167.40	$1,167.30