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	$85.25	3.520%	$88.2508	$88.25	$88.25	$88.30
Purchase #2	$243.34	9.827%	$267.253	$267.25	$267.25	$267.30
Purchase #3	$164.69	8.311%	$178.3774	$178.38	$178.40	$178.40
Purchase #4	$31.40	12.366%	$35.2829	$35.28	$35.30	$35.30
Purchase #5	$67.41	8.374%	$73.0549	$73.05	$73.05	$73.10
Purchase #6	$193.94	11.281%	$215.8184	$215.82	$215.80	$215.80
Purchase #7	$81.91	9.297%	$89.5252	$89.53	$89.55	$89.50
7 purchase totals =	$867.94		$947.5626	$947.56	$947.60	$947.70