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	$179.40	9.322%	$196.1237	$196.12	$196.10	$196.10
Purchase #2	$50.72	7.786%	$54.6691	$54.67	$54.65	$54.70
Purchase #3	$101.96	13.626%	$115.8531	$115.85	$115.85	$115.90
Purchase #4	$134.89	6.840%	$144.1165	$144.12	$144.10	$144.10
Purchase #5	$99.90	7.732%	$107.6243	$107.62	$107.60	$107.60
Purchase #6	$79.75	7.175%	$85.4721	$85.47	$85.45	$85.50
Purchase #7	$196.97	3.351%	$203.5705	$203.57	$203.55	$203.60
7 purchase totals =	$843.59		$907.4293	$907.42	$907.30	$907.50