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	$43.33	9.106%	$47.2756	$47.28	$47.30	$47.30
Purchase #2	$57.68	11.622%	$64.3836	$64.38	$64.40	$64.40
Purchase #3	$38.68	10.480%	$42.7337	$42.73	$42.75	$42.70
Purchase #4	$216.76	7.757%	$233.5741	$233.57	$233.55	$233.60
Purchase #5	$96.70	3.391%	$99.9791	$99.98	$100.00	$100.00
Purchase #6	$68.64	11.620%	$76.616	$76.62	$76.60	$76.60
Purchase #7	$221.89	7.320%	$238.1323	$238.13	$238.15	$238.10
7 purchase totals =	$743.68		$802.6944	$802.69	$802.75	$802.70