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	$173.75	13.321%	$196.8952	$196.90	$196.90	$196.90
Purchase #2	$122.68	13.294%	$138.9891	$138.99	$139.00	$139.00
Purchase #3	$170.62	11.755%	$190.6764	$190.68	$190.70	$190.70
Purchase #4	$227.74	3.320%	$235.301	$235.30	$235.30	$235.30
Purchase #5	$89.62	8.152%	$96.9258	$96.93	$96.95	$96.90
Purchase #6	$171.63	11.784%	$191.8549	$191.85	$191.85	$191.90
Purchase #7	$82.70	8.770%	$89.9528	$89.95	$89.95	$90.00
7 purchase totals =	$1,038.74		$1,140.5952	$1,140.60	$1,140.65	$1,140.70