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	$168.26	3.393%	$173.9691	$173.97	$173.95	$174.00
Purchase #2	$131.54	5.744%	$139.0957	$139.10	$139.10	$139.10
Purchase #3	$73.84	9.233%	$80.6576	$80.66	$80.65	$80.70
Purchase #4	$37.32	3.228%	$38.5247	$38.52	$38.50	$38.50
Purchase #5	$98.63	7.358%	$105.8872	$105.89	$105.90	$105.90
Purchase #6	$27.26	4.781%	$28.5633	$28.56	$28.55	$28.60
Purchase #7	$214.46	8.820%	$233.3754	$233.38	$233.40	$233.40
7 purchase totals =	$751.31		$800.0730	$800.08	$800.05	$800.20