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	$33.43	4.705%	$35.0029	$35.00	$35.00	$35.00
Purchase #2	$64.34	12.607%	$72.4513	$72.45	$72.45	$72.50
Purchase #3	$171.76	9.856%	$188.6887	$188.69	$188.70	$188.70
Purchase #4	$206.88	13.660%	$235.1398	$235.14	$235.15	$235.10
Purchase #5	$162.34	3.426%	$167.9018	$167.90	$167.90	$167.90
Purchase #6	$70.55	3.480%	$73.0051	$73.01	$73.00	$73.00
Purchase #7	$218.72	4.859%	$229.3476	$229.35	$229.35	$229.30
7 purchase totals =	$928.02		$1,001.5372	$1,001.54	$1,001.55	$1,001.50