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	$219.72	6.863%	$234.7994	$234.80	$234.80	$234.80
Purchase #2	$67.26	8.801%	$73.1796	$73.18	$73.20	$73.20
Purchase #3	$28.69	10.303%	$31.6459	$31.65	$31.65	$31.60
Purchase #4	$137.34	8.181%	$148.5758	$148.58	$148.60	$148.60
Purchase #5	$30.60	4.578%	$32.0009	$32.00	$32.00	$32.00
Purchase #6	$202.73	9.652%	$222.2975	$222.30	$222.30	$222.30
Purchase #7	$44.45	3.242%	$45.8911	$45.89	$45.90	$45.90
7 purchase totals =	$730.79		$788.3902	$788.40	$788.45	$788.40