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	$221.93	3.221%	$229.0784	$229.08	$229.10	$229.10
Purchase #2	$67.93	7.136%	$72.7775	$72.78	$72.80	$72.80
Purchase #3	$61.41	3.493%	$63.5551	$63.56	$63.55	$63.60
Purchase #4	$99.90	8.463%	$108.3545	$108.35	$108.35	$108.40
Purchase #5	$95.90	7.655%	$103.2411	$103.24	$103.25	$103.20
Purchase #6	$101.33	4.494%	$105.8838	$105.88	$105.90	$105.90
Purchase #7	$35.95	13.222%	$40.7033	$40.70	$40.70	$40.70
7 purchase totals =	$684.35		$723.5937	$723.59	$723.65	$723.70