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	$89.25	3.678%	$92.5326	$92.53	$92.55	$92.50
Purchase #2	$181.59	4.384%	$189.5509	$189.55	$189.55	$189.60
Purchase #3	$139.52	8.663%	$151.6066	$151.61	$151.60	$151.60
Purchase #4	$194.83	6.286%	$207.077	$207.08	$207.10	$207.10
Purchase #5	$42.34	7.335%	$45.4456	$45.45	$45.45	$45.40
Purchase #6	$221.25	3.473%	$228.934	$228.93	$228.95	$228.90
Purchase #7	$93.31	4.434%	$97.4474	$97.45	$97.45	$97.40
7 purchase totals =	$962.09		$1,012.5941	$1,012.60	$1,012.65	$1,012.50