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	$57.43	3.708%	$59.5595	$59.56	$59.55	$59.60
Purchase #2	$233.88	11.778%	$261.4264	$261.43	$261.45	$261.40
Purchase #3	$5.70	10.620%	$6.3053	$6.31	$6.30	$6.30
Purchase #4	$196.35	3.674%	$203.5639	$203.56	$203.55	$203.60
Purchase #5	$139.56	11.826%	$156.0644	$156.06	$156.05	$156.10
Purchase #6	$33.57	6.323%	$35.6926	$35.69	$35.70	$35.70
Purchase #7	$165.27	10.386%	$182.4349	$182.43	$182.45	$182.40
7 purchase totals =	$831.76		$905.0470	$905.04	$905.05	$905.10