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	$20.27	4.830%	$21.249	$21.25	$21.25	$21.20
Purchase #2	$31.36	6.418%	$33.3727	$33.37	$33.35	$33.40
Purchase #3	$160.78	6.375%	$171.0297	$171.03	$171.05	$171.00
Purchase #4	$224.86	9.281%	$245.7293	$245.73	$245.75	$245.70
Purchase #5	$161.29	7.376%	$173.1868	$173.19	$173.20	$173.20
Purchase #6	$132.84	10.349%	$146.5876	$146.59	$146.60	$146.60
Purchase #7	$241.35	9.564%	$264.4327	$264.43	$264.45	$264.40
7 purchase totals =	$972.75		$1,055.5878	$1,055.59	$1,055.65	$1,055.50