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	$193.31	7.319%	$207.4584	$207.46	$207.45	$207.50
Purchase #2	$28.63	10.493%	$31.6341	$31.63	$31.65	$31.60
Purchase #3	$241.33	3.302%	$249.2987	$249.30	$249.30	$249.30
Purchase #4	$181.31	10.220%	$199.8399	$199.84	$199.85	$199.80
Purchase #5	$83.92	6.610%	$89.4671	$89.47	$89.45	$89.50
Purchase #6	$153.41	3.338%	$158.5308	$158.53	$158.55	$158.50
Purchase #7	$38.82	10.535%	$42.9097	$42.91	$42.90	$42.90
7 purchase totals =	$920.73		$979.1387	$979.14	$979.15	$979.10