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	$162.55	5.620%	$171.6853	$171.69	$171.70	$171.70
Purchase #2	$33.98	4.329%	$35.451	$35.45	$35.45	$35.50
Purchase #3	$234.77	13.240%	$265.8535	$265.85	$265.85	$265.90
Purchase #4	$194.92	9.666%	$213.761	$213.76	$213.75	$213.80
Purchase #5	$196.56	4.378%	$205.1654	$205.17	$205.15	$205.20
Purchase #6	$67.40	8.239%	$72.9531	$72.95	$72.95	$73.00
Purchase #7	$35.27	12.260%	$39.5941	$39.59	$39.60	$39.60
7 purchase totals =	$925.45		$1,004.4634	$1,004.46	$1,004.45	$1,004.70