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	$5.71	4.152%	$5.9471	$5.95	$5.95	$5.90
Purchase #2	$84.38	7.817%	$90.976	$90.98	$91.00	$91.00
Purchase #3	$171.82	8.338%	$186.1464	$186.15	$186.15	$186.10
Purchase #4	$54.73	11.650%	$61.106	$61.11	$61.10	$61.10
Purchase #5	$92.47	13.105%	$104.5882	$104.59	$104.60	$104.60
Purchase #6	$20.81	13.746%	$23.6705	$23.67	$23.65	$23.70
Purchase #7	$205.95	7.820%	$222.0553	$222.06	$222.05	$222.10
7 purchase totals =	$635.87		$694.4895	$694.51	$694.50	$694.50