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	$76.29	9.687%	$83.6802	$83.68	$83.70	$83.70
Purchase #2	$79.77	12.755%	$89.9447	$89.94	$89.95	$89.90
Purchase #3	$21.83	3.746%	$22.6478	$22.65	$22.65	$22.60
Purchase #4	$52.31	10.735%	$57.9255	$57.93	$57.95	$57.90
Purchase #5	$69.86	4.229%	$72.8144	$72.81	$72.80	$72.80
Purchase #6	$102.57	3.654%	$106.3179	$106.32	$106.30	$106.30
Purchase #7	$92.30	6.208%	$98.03	$98.03	$98.05	$98.00
7 purchase totals =	$494.93		$531.3605	$531.36	$531.40	$531.20