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	$165.51	3.347%	$171.0496	$171.05	$171.05	$171.00
Purchase #2	$249.67	3.565%	$258.5707	$258.57	$258.55	$258.60
Purchase #3	$172.68	10.242%	$190.3659	$190.37	$190.35	$190.40
Purchase #4	$18.51	10.568%	$20.4661	$20.47	$20.45	$20.50
Purchase #5	$55.84	11.549%	$62.289	$62.29	$62.30	$62.30
Purchase #6	$161.71	4.686%	$169.2877	$169.29	$169.30	$169.30
Purchase #7	$125.38	10.482%	$138.5223	$138.52	$138.50	$138.50
7 purchase totals =	$949.30		$1,010.5513	$1,010.56	$1,010.50	$1,010.60