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	$86.76	6.512%	$92.4098	$92.41	$92.40	$92.40
Purchase #2	$233.92	3.318%	$241.6815	$241.68	$241.70	$241.70
Purchase #3	$117.59	12.309%	$132.0642	$132.06	$132.05	$132.10
Purchase #4	$108.75	13.162%	$123.0637	$123.06	$123.05	$123.10
Purchase #5	$90.28	7.334%	$96.9011	$96.90	$96.90	$96.90
Purchase #6	$221.89	7.441%	$238.4008	$238.40	$238.40	$238.40
Purchase #7	$143.76	11.782%	$160.6978	$160.70	$160.70	$160.70
7 purchase totals =	$1,002.95		$1,085.2189	$1,085.21	$1,085.20	$1,085.30