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	$69.60	9.839%	$76.4479	$76.45	$76.45	$76.40
Purchase #2	$54.64	8.119%	$59.0762	$59.08	$59.10	$59.10
Purchase #3	$5.29	5.629%	$5.5878	$5.59	$5.60	$5.60
Purchase #4	$167.60	11.646%	$187.1187	$187.12	$187.10	$187.10
Purchase #5	$38.96	6.855%	$41.6307	$41.63	$41.65	$41.60
Purchase #6	$83.99	7.137%	$89.9844	$89.98	$90.00	$90.00
Purchase #7	$236.39	7.252%	$253.533	$253.53	$253.55	$253.50
7 purchase totals =	$656.47		$713.3787	$713.38	$713.45	$713.30