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	$148.76	3.870%	$154.517	$154.52	$154.50	$154.50
Purchase #2	$134.42	8.847%	$146.3121	$146.31	$146.30	$146.30
Purchase #3	$160.47	3.384%	$165.9003	$165.90	$165.90	$165.90
Purchase #4	$207.45	6.558%	$221.0546	$221.05	$221.05	$221.10
Purchase #5	$66.89	7.456%	$71.8773	$71.88	$71.90	$71.90
Purchase #6	$99.38	9.861%	$109.1799	$109.18	$109.20	$109.20
Purchase #7	$119.42	7.720%	$128.6392	$128.64	$128.65	$128.60
7 purchase totals =	$936.79		$997.4804	$997.48	$997.50	$997.50