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	$94.80	5.432%	$99.9495	$99.95	$99.95	$99.90
Purchase #2	$52.89	3.302%	$54.6364	$54.64	$54.65	$54.60
Purchase #3	$124.94	4.856%	$131.0071	$131.01	$131.00	$131.00
Purchase #4	$247.99	6.116%	$263.1571	$263.16	$263.15	$263.20
Purchase #5	$236.54	13.107%	$267.5433	$267.54	$267.55	$267.50
Purchase #6	$156.44	4.104%	$162.8603	$162.86	$162.85	$162.90
Purchase #7	$126.64	13.216%	$143.3767	$143.38	$143.40	$143.40
7 purchase totals =	$1,040.24		$1,122.5304	$1,122.54	$1,122.55	$1,122.50