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	$10.91	7.748%	$11.7553	$11.76	$11.75	$11.80
Purchase #2	$43.44	6.507%	$46.2666	$46.27	$46.25	$46.30
Purchase #3	$82.98	4.665%	$86.851	$86.85	$86.85	$86.90
Purchase #4	$18.53	13.781%	$21.0836	$21.08	$21.10	$21.10
Purchase #5	$99.27	5.709%	$104.9373	$104.94	$104.95	$104.90
Purchase #6	$238.98	4.837%	$250.5395	$250.54	$250.55	$250.50
Purchase #7	$178.98	6.149%	$189.9855	$189.99	$190.00	$190.00
7 purchase totals =	$673.09		$711.4188	$711.43	$711.45	$711.50