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	$177.84	10.428%	$196.3852	$196.39	$196.40	$196.40
Purchase #2	$17.99	11.236%	$20.0114	$20.01	$20.00	$20.00
Purchase #3	$183.31	3.736%	$190.1585	$190.16	$190.15	$190.20
Purchase #4	$220.91	12.278%	$248.0333	$248.03	$248.05	$248.00
Purchase #5	$156.73	7.363%	$168.27	$168.27	$168.25	$168.30
Purchase #6	$32.26	4.854%	$33.8259	$33.83	$33.85	$33.80
Purchase #7	$86.42	5.254%	$90.9605	$90.96	$90.95	$91.00
7 purchase totals =	$875.46		$947.6448	$947.65	$947.65	$947.70