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	$205.47	6.245%	$218.3016	$218.30	$218.30	$218.30
Purchase #2	$79.75	11.609%	$89.0082	$89.01	$89.00	$89.00
Purchase #3	$82.48	6.850%	$88.1299	$88.13	$88.15	$88.10
Purchase #4	$57.50	8.484%	$62.3783	$62.38	$62.40	$62.40
Purchase #5	$181.39	12.285%	$203.6738	$203.67	$203.65	$203.70
Purchase #6	$94.41	6.525%	$100.5703	$100.57	$100.55	$100.60
Purchase #7	$123.49	9.224%	$134.8807	$134.88	$134.90	$134.90
7 purchase totals =	$824.49		$896.9428	$896.94	$896.95	$897.00