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	$19.80	12.738%	$22.3221	$22.32	$22.30	$22.30
Purchase #2	$182.89	6.444%	$194.6754	$194.68	$194.70	$194.70
Purchase #3	$64.87	4.231%	$67.6146	$67.61	$67.60	$67.60
Purchase #4	$52.73	6.450%	$56.1311	$56.13	$56.15	$56.10
Purchase #5	$247.91	4.287%	$258.5379	$258.54	$258.55	$258.50
Purchase #6	$61.59	5.746%	$65.129	$65.13	$65.15	$65.10
Purchase #7	$178.34	11.851%	$199.4751	$199.48	$199.50	$199.50
7 purchase totals =	$808.13		$863.8852	$863.89	$863.95	$863.80