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	$208.59	10.709%	$230.9279	$230.93	$230.95	$230.90
Purchase #2	$94.87	4.819%	$99.4418	$99.44	$99.45	$99.40
Purchase #3	$138.50	13.115%	$156.6643	$156.66	$156.65	$156.70
Purchase #4	$71.80	10.734%	$79.507	$79.51	$79.50	$79.50
Purchase #5	$138.45	9.834%	$152.0652	$152.07	$152.05	$152.10
Purchase #6	$238.45	6.708%	$254.4452	$254.45	$254.45	$254.40
Purchase #7	$233.66	9.328%	$255.4558	$255.46	$255.45	$255.50
7 purchase totals =	$1,124.32		$1,228.5072	$1,228.52	$1,228.50	$1,228.50