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	$45.46	6.117%	$48.2408	$48.24	$48.25	$48.20
Purchase #2	$146.69	12.243%	$164.6493	$164.65	$164.65	$164.60
Purchase #3	$50.43	6.261%	$53.5874	$53.59	$53.60	$53.60
Purchase #4	$196.83	5.816%	$208.2776	$208.28	$208.30	$208.30
Purchase #5	$198.83	4.469%	$207.7157	$207.72	$207.70	$207.70
Purchase #6	$179.69	11.674%	$200.667	$200.67	$200.65	$200.70
Purchase #7	$114.36	12.481%	$128.6333	$128.63	$128.65	$128.60
7 purchase totals =	$932.29		$1,011.7711	$1,011.78	$1,011.80	$1,011.70