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	$192.66	10.670%	$213.2168	$213.22	$213.20	$213.20
Purchase #2	$82.44	4.788%	$86.3872	$86.39	$86.40	$86.40
Purchase #3	$28.85	7.630%	$31.0513	$31.05	$31.05	$31.10
Purchase #4	$62.79	3.762%	$65.1522	$65.15	$65.15	$65.20
Purchase #5	$181.88	13.486%	$206.4083	$206.41	$206.40	$206.40
Purchase #6	$180.37	9.119%	$196.8179	$196.82	$196.80	$196.80
Purchase #7	$134.32	11.162%	$149.3128	$149.31	$149.30	$149.30
7 purchase totals =	$863.31		$948.3465	$948.35	$948.30	$948.40