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	$31.64	12.204%	$35.5013	$35.50	$35.50	$35.50
Purchase #2	$245.54	6.407%	$261.2717	$261.27	$261.25	$261.30
Purchase #3	$81.77	5.675%	$86.4104	$86.41	$86.40	$86.40
Purchase #4	$104.34	12.833%	$117.73	$117.73	$117.75	$117.70
Purchase #5	$156.90	6.145%	$166.5415	$166.54	$166.55	$166.50
Purchase #6	$50.36	5.120%	$52.9384	$52.94	$52.95	$52.90
Purchase #7	$89.31	5.648%	$94.3542	$94.35	$94.35	$94.40
7 purchase totals =	$759.86		$814.7475	$814.74	$814.75	$814.70