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	$77.42	4.668%	$81.034	$81.03	$81.05	$81.00
Purchase #2	$85.45	7.638%	$91.9767	$91.98	$92.00	$92.00
Purchase #3	$219.83	10.608%	$243.1496	$243.15	$243.15	$243.10
Purchase #4	$73.28	10.108%	$80.6871	$80.69	$80.70	$80.70
Purchase #5	$39.95	9.308%	$43.6685	$43.67	$43.65	$43.70
Purchase #6	$158.94	3.515%	$164.5267	$164.53	$164.55	$164.50
Purchase #7	$156.98	6.595%	$167.3328	$167.33	$167.35	$167.30
7 purchase totals =	$811.85		$872.3754	$872.38	$872.45	$872.30