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	$145.38	13.540%	$165.0645	$165.06	$165.05	$165.10
Purchase #2	$128.75	5.872%	$136.3102	$136.31	$136.30	$136.30
Purchase #3	$246.98	10.787%	$273.6217	$273.62	$273.60	$273.60
Purchase #4	$131.97	6.362%	$140.3659	$140.37	$140.35	$140.40
Purchase #5	$225.53	13.206%	$255.3135	$255.31	$255.30	$255.30
Purchase #6	$31.82	11.362%	$35.4354	$35.44	$35.45	$35.40
Purchase #7	$143.28	6.459%	$152.5345	$152.53	$152.55	$152.50
7 purchase totals =	$1,053.71		$1,158.6457	$1,158.64	$1,158.60	$1,158.60