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	$165.57	3.660%	$171.6299	$171.63	$171.65	$171.60
Purchase #2	$28.33	11.149%	$31.4885	$31.49	$31.50	$31.50
Purchase #3	$170.85	4.222%	$178.0633	$178.06	$178.05	$178.10
Purchase #4	$179.57	11.388%	$200.0194	$200.02	$200.00	$200.00
Purchase #5	$71.72	13.792%	$81.6116	$81.61	$81.60	$81.60
Purchase #6	$216.71	10.745%	$239.9955	$240.00	$240.00	$240.00
Purchase #7	$91.92	6.832%	$98.2	$98.20	$98.20	$98.20
7 purchase totals =	$924.67		$1,001.0082	$1,001.01	$1,001.00	$1,001.00