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	$162.33	11.681%	$181.2918	$181.29	$181.30	$181.30
Purchase #2	$9.41	9.748%	$10.3273	$10.33	$10.35	$10.30
Purchase #3	$137.86	9.715%	$151.2531	$151.25	$151.25	$151.30
Purchase #4	$227.33	9.751%	$249.4969	$249.50	$249.50	$249.50
Purchase #5	$218.47	5.846%	$231.2418	$231.24	$231.25	$231.20
Purchase #6	$38.59	11.134%	$42.8866	$42.89	$42.90	$42.90
Purchase #7	$200.43	10.165%	$220.8037	$220.80	$220.80	$220.80
7 purchase totals =	$994.42		$1,087.3012	$1,087.30	$1,087.35	$1,087.30