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	$70.94	10.413%	$78.327	$78.33	$78.35	$78.30
Purchase #2	$192.46	3.311%	$198.8324	$198.83	$198.85	$198.80
Purchase #3	$11.39	12.417%	$12.8043	$12.80	$12.80	$12.80
Purchase #4	$246.45	6.613%	$262.7477	$262.75	$262.75	$262.70
Purchase #5	$36.40	5.282%	$38.3226	$38.32	$38.30	$38.30
Purchase #6	$99.32	5.158%	$104.4429	$104.44	$104.45	$104.40
Purchase #7	$34.80	5.805%	$36.8201	$36.82	$36.80	$36.80
7 purchase totals =	$691.76		$732.2970	$732.29	$732.30	$732.10