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	$85.48	5.837%	$90.4695	$90.47	$90.45	$90.50
Purchase #2	$13.78	12.146%	$15.4537	$15.45	$15.45	$15.50
Purchase #3	$234.79	3.507%	$243.0241	$243.02	$243.00	$243.00
Purchase #4	$96.77	10.759%	$107.1815	$107.18	$107.20	$107.20
Purchase #5	$240.69	6.181%	$255.567	$255.57	$255.55	$255.60
Purchase #6	$51.26	9.382%	$56.0692	$56.07	$56.05	$56.10
Purchase #7	$207.87	12.231%	$233.2946	$233.29	$233.30	$233.30
7 purchase totals =	$930.64		$1,001.0596	$1,001.05	$1,001.00	$1,001.20