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	$219.91	5.465%	$231.9281	$231.93	$231.95	$231.90
Purchase #2	$134.64	4.424%	$140.5965	$140.60	$140.60	$140.60
Purchase #3	$79.91	11.753%	$89.3018	$89.30	$89.30	$89.30
Purchase #4	$210.72	10.843%	$233.5684	$233.57	$233.55	$233.60
Purchase #5	$107.86	4.481%	$112.6932	$112.69	$112.70	$112.70
Purchase #6	$186.35	13.495%	$211.4979	$211.50	$211.50	$211.50
Purchase #7	$248.44	9.624%	$272.3499	$272.35	$272.35	$272.30
7 purchase totals =	$1,187.83		$1,291.9358	$1,291.94	$1,291.95	$1,291.90