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	$74.74	10.127%	$82.3089	$82.31	$82.30	$82.30
Purchase #2	$179.41	8.560%	$194.7675	$194.77	$194.75	$194.80
Purchase #3	$108.41	3.318%	$112.007	$112.01	$112.00	$112.00
Purchase #4	$216.61	6.863%	$231.4759	$231.48	$231.50	$231.50
Purchase #5	$182.56	6.358%	$194.1672	$194.17	$194.15	$194.20
Purchase #6	$164.31	9.424%	$179.7946	$179.79	$179.80	$179.80
Purchase #7	$103.51	5.755%	$109.467	$109.47	$109.45	$109.50
7 purchase totals =	$1,029.55		$1,103.9881	$1,104.00	$1,103.95	$1,104.10