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	$175.60	3.467%	$181.6881	$181.69	$181.70	$181.70
Purchase #2	$90.61	6.210%	$96.2369	$96.24	$96.25	$96.20
Purchase #3	$246.88	13.494%	$280.194	$280.19	$280.20	$280.20
Purchase #4	$77.54	6.385%	$82.4909	$82.49	$82.50	$82.50
Purchase #5	$229.94	3.309%	$237.5487	$237.55	$237.55	$237.50
Purchase #6	$92.42	4.528%	$96.6048	$96.60	$96.60	$96.60
Purchase #7	$94.61	13.788%	$107.6548	$107.65	$107.65	$107.70
7 purchase totals =	$1,007.60		$1,082.4182	$1,082.41	$1,082.45	$1,082.40