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	$153.30	8.154%	$165.8001	$165.80	$165.80	$165.80
Purchase #2	$48.54	4.816%	$50.8777	$50.88	$50.90	$50.90
Purchase #3	$154.50	6.157%	$164.0126	$164.01	$164.00	$164.00
Purchase #4	$38.46	10.525%	$42.5079	$42.51	$42.50	$42.50
Purchase #5	$191.39	3.600%	$198.28	$198.28	$198.30	$198.30
Purchase #6	$175.30	6.488%	$186.6735	$186.67	$186.65	$186.70
Purchase #7	$162.82	6.481%	$173.3724	$173.37	$173.35	$173.40
7 purchase totals =	$924.31		$981.5242	$981.52	$981.50	$981.60