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	$146.62	12.115%	$164.383	$164.38	$164.40	$164.40
Purchase #2	$69.37	5.251%	$73.0126	$73.01	$73.00	$73.00
Purchase #3	$152.66	9.670%	$167.4222	$167.42	$167.40	$167.40
Purchase #4	$70.85	7.671%	$76.2849	$76.28	$76.30	$76.30
Purchase #5	$190.40	13.731%	$216.5438	$216.54	$216.55	$216.50
Purchase #6	$88.36	12.372%	$99.2919	$99.29	$99.30	$99.30
Purchase #7	$53.92	11.124%	$59.9181	$59.92	$59.90	$59.90
7 purchase totals =	$772.18		$856.8565	$856.84	$856.85	$856.80