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	$137.41	13.785%	$156.352	$156.35	$156.35	$156.40
Purchase #2	$142.42	7.502%	$153.1043	$153.10	$153.10	$153.10
Purchase #3	$19.80	12.616%	$22.298	$22.30	$22.30	$22.30
Purchase #4	$72.47	8.455%	$78.5973	$78.60	$78.60	$78.60
Purchase #5	$200.75	11.618%	$224.0731	$224.07	$224.05	$224.10
Purchase #6	$19.75	8.301%	$21.3894	$21.39	$21.40	$21.40
Purchase #7	$73.71	3.553%	$76.3289	$76.33	$76.35	$76.30
7 purchase totals =	$666.31		$732.1430	$732.14	$732.15	$732.20