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	$76.73	12.626%	$86.4179	$86.42	$86.40	$86.40
Purchase #2	$234.97	13.783%	$267.3559	$267.36	$267.35	$267.40
Purchase #3	$71.46	11.423%	$79.6229	$79.62	$79.60	$79.60
Purchase #4	$99.98	11.456%	$111.4337	$111.43	$111.45	$111.40
Purchase #5	$49.29	10.154%	$54.2949	$54.29	$54.30	$54.30
Purchase #6	$190.59	4.170%	$198.5376	$198.54	$198.55	$198.50
Purchase #7	$166.70	12.563%	$187.6425	$187.64	$187.65	$187.60
7 purchase totals =	$889.72		$985.3054	$985.30	$985.30	$985.20