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	$90.64	4.149%	$94.4007	$94.40	$94.40	$94.40
Purchase #2	$238.75	9.647%	$261.7822	$261.78	$261.80	$261.80
Purchase #3	$27.71	12.591%	$31.199	$31.20	$31.20	$31.20
Purchase #4	$82.76	7.259%	$88.7675	$88.77	$88.75	$88.80
Purchase #5	$62.68	13.671%	$71.249	$71.25	$71.25	$71.20
Purchase #6	$177.60	10.545%	$196.3279	$196.33	$196.35	$196.30
Purchase #7	$79.45	12.264%	$89.1937	$89.19	$89.20	$89.20
7 purchase totals =	$759.59		$832.9200	$832.92	$832.95	$832.90