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	$241.56	9.635%	$264.8343	$264.83	$264.85	$264.80
Purchase #2	$19.59	9.766%	$21.5032	$21.50	$21.50	$21.50
Purchase #3	$136.48	5.860%	$144.4777	$144.48	$144.50	$144.50
Purchase #4	$91.68	12.655%	$103.2821	$103.28	$103.30	$103.30
Purchase #5	$5.93	10.155%	$6.5322	$6.53	$6.55	$6.50
Purchase #6	$45.32	3.168%	$46.7557	$46.76	$46.75	$46.80
Purchase #7	$167.49	5.608%	$176.8828	$176.88	$176.90	$176.90
7 purchase totals =	$708.05		$764.2680	$764.26	$764.35	$764.30