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	$174.37	3.509%	$180.4886	$180.49	$180.50	$180.50
Purchase #2	$19.87	4.251%	$20.7147	$20.71	$20.70	$20.70
Purchase #3	$225.60	8.869%	$245.6085	$245.61	$245.60	$245.60
Purchase #4	$31.94	7.874%	$34.455	$34.46	$34.45	$34.50
Purchase #5	$74.30	10.783%	$82.3118	$82.31	$82.30	$82.30
Purchase #6	$88.73	4.649%	$92.8551	$92.86	$92.85	$92.90
Purchase #7	$89.87	7.745%	$96.8304	$96.83	$96.85	$96.80
7 purchase totals =	$704.68		$753.2641	$753.27	$753.25	$753.30