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	$147.67	12.714%	$166.4448	$166.44	$166.45	$166.40
Purchase #2	$97.96	7.237%	$105.0494	$105.05	$105.05	$105.00
Purchase #3	$245.31	11.404%	$273.2852	$273.29	$273.30	$273.30
Purchase #4	$212.41	4.254%	$221.4459	$221.45	$221.45	$221.40
Purchase #5	$125.71	12.107%	$140.9297	$140.93	$140.95	$140.90
Purchase #6	$106.43	6.631%	$113.4874	$113.49	$113.50	$113.50
Purchase #7	$77.82	6.521%	$82.8946	$82.89	$82.90	$82.90
7 purchase totals =	$1,013.31		$1,103.5370	$1,103.54	$1,103.60	$1,103.40