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	$31.52	3.473%	$32.6147	$32.61	$32.60	$32.60
Purchase #2	$85.69	4.253%	$89.3344	$89.33	$89.35	$89.30
Purchase #3	$249.71	5.565%	$263.6064	$263.61	$263.60	$263.60
Purchase #4	$207.78	9.156%	$226.8043	$226.80	$226.80	$226.80
Purchase #5	$171.87	12.375%	$193.1389	$193.14	$193.15	$193.10
Purchase #6	$59.32	6.148%	$62.967	$62.97	$62.95	$63.00
Purchase #7	$124.87	12.740%	$140.7784	$140.78	$140.80	$140.80
7 purchase totals =	$930.76		$1,009.2441	$1,009.24	$1,009.25	$1,009.20