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	$103.85	10.509%	$114.7636	$114.76	$114.75	$114.80
Purchase #2	$56.61	4.245%	$59.0131	$59.01	$59.00	$59.00
Purchase #3	$164.82	10.585%	$182.2662	$182.27	$182.25	$182.30
Purchase #4	$150.51	9.521%	$164.8401	$164.84	$164.85	$164.80
Purchase #5	$62.65	8.126%	$67.7409	$67.74	$67.75	$67.70
Purchase #6	$75.59	12.419%	$84.9775	$84.98	$85.00	$85.00
Purchase #7	$127.39	6.220%	$135.3137	$135.31	$135.30	$135.30
7 purchase totals =	$741.42		$808.9151	$808.91	$808.90	$808.90