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	$214.37	3.351%	$221.5535	$221.55	$221.55	$221.60
Purchase #2	$63.81	12.659%	$71.8877	$71.89	$71.90	$71.90
Purchase #3	$192.38	10.874%	$213.2994	$213.30	$213.30	$213.30
Purchase #4	$66.88	10.691%	$74.0301	$74.03	$74.05	$74.00
Purchase #5	$28.60	13.471%	$32.4527	$32.45	$32.45	$32.50
Purchase #6	$79.82	3.150%	$82.3343	$82.33	$82.35	$82.30
Purchase #7	$105.98	13.802%	$120.6074	$120.61	$120.60	$120.60
7 purchase totals =	$751.84		$816.1651	$816.16	$816.20	$816.20