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	$90.29	3.788%	$93.7102	$93.71	$93.70	$93.70
Purchase #2	$162.50	11.665%	$181.4556	$181.46	$181.45	$181.50
Purchase #3	$200.66	6.627%	$213.9577	$213.96	$213.95	$214.00
Purchase #4	$138.89	7.449%	$149.2359	$149.24	$149.25	$149.20
Purchase #5	$89.37	11.383%	$99.543	$99.54	$99.55	$99.50
Purchase #6	$206.61	4.430%	$215.7628	$215.76	$215.75	$215.80
Purchase #7	$84.31	5.764%	$89.1696	$89.17	$89.15	$89.20
7 purchase totals =	$972.63		$1,042.8348	$1,042.84	$1,042.80	$1,042.90