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	$170.34	6.614%	$181.6063	$181.61	$181.60	$181.60
Purchase #2	$88.77	11.801%	$99.2457	$99.25	$99.25	$99.20
Purchase #3	$190.86	7.616%	$205.3959	$205.40	$205.40	$205.40
Purchase #4	$216.52	3.248%	$223.5526	$223.55	$223.55	$223.60
Purchase #5	$70.56	4.831%	$73.9688	$73.97	$73.95	$74.00
Purchase #6	$107.38	10.449%	$118.6001	$118.60	$118.60	$118.60
Purchase #7	$121.41	4.664%	$127.0726	$127.07	$127.05	$127.10
7 purchase totals =	$965.84		$1,029.4420	$1,029.45	$1,029.40	$1,029.50