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	$177.79	10.576%	$196.5931	$196.59	$196.60	$196.60
Purchase #2	$95.44	3.360%	$98.6468	$98.65	$98.65	$98.60
Purchase #3	$152.51	12.324%	$171.3053	$171.31	$171.30	$171.30
Purchase #4	$76.61	3.419%	$79.2293	$79.23	$79.25	$79.20
Purchase #5	$191.57	13.224%	$216.9032	$216.90	$216.90	$216.90
Purchase #6	$41.66	12.638%	$46.925	$46.93	$46.95	$46.90
Purchase #7	$92.51	7.540%	$99.4853	$99.49	$99.50	$99.50
7 purchase totals =	$828.09		$909.0880	$909.10	$909.15	$909.00