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	$73.87	11.191%	$82.1368	$82.14	$82.15	$82.10
Purchase #2	$48.46	12.756%	$54.6416	$54.64	$54.65	$54.60
Purchase #3	$197.74	13.200%	$223.8417	$223.84	$223.85	$223.80
Purchase #4	$163.51	3.692%	$169.5468	$169.55	$169.55	$169.50
Purchase #5	$176.76	3.720%	$183.3355	$183.34	$183.35	$183.30
Purchase #6	$98.88	6.542%	$105.3487	$105.35	$105.35	$105.30
Purchase #7	$131.63	10.364%	$145.2721	$145.27	$145.25	$145.30
7 purchase totals =	$890.85		$964.1232	$964.13	$964.15	$963.90