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	$78.74	9.814%	$86.4675	$86.47	$86.45	$86.50
Purchase #2	$134.39	5.577%	$141.8849	$141.88	$141.90	$141.90
Purchase #3	$87.73	13.818%	$99.8525	$99.85	$99.85	$99.90
Purchase #4	$150.47	12.414%	$169.1493	$169.15	$169.15	$169.10
Purchase #5	$249.89	3.472%	$258.5662	$258.57	$258.55	$258.60
Purchase #6	$157.25	4.632%	$164.5338	$164.53	$164.55	$164.50
Purchase #7	$170.41	4.516%	$178.1057	$178.11	$178.10	$178.10
7 purchase totals =	$1,028.88		$1,098.5599	$1,098.56	$1,098.55	$1,098.60