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	$101.65	13.161%	$115.0282	$115.03	$115.05	$115.00
Purchase #2	$93.54	3.496%	$96.8102	$96.81	$96.80	$96.80
Purchase #3	$28.92	9.463%	$31.6567	$31.66	$31.65	$31.70
Purchase #4	$182.97	7.260%	$196.2536	$196.25	$196.25	$196.30
Purchase #5	$210.64	12.445%	$236.8541	$236.85	$236.85	$236.90
Purchase #6	$154.55	7.685%	$166.4272	$166.43	$166.45	$166.40
Purchase #7	$55.94	6.194%	$59.4049	$59.40	$59.40	$59.40
7 purchase totals =	$828.21		$902.4349	$902.43	$902.45	$902.50