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	$117.82	5.282%	$124.0433	$124.04	$124.05	$124.00
Purchase #2	$239.82	3.471%	$248.1442	$248.14	$248.15	$248.10
Purchase #3	$142.59	12.476%	$160.3795	$160.38	$160.40	$160.40
Purchase #4	$194.60	4.325%	$203.0165	$203.02	$203.00	$203.00
Purchase #5	$156.72	9.311%	$171.3122	$171.31	$171.30	$171.30
Purchase #6	$123.67	5.362%	$130.3012	$130.30	$130.30	$130.30
Purchase #7	$92.59	8.359%	$100.3296	$100.33	$100.35	$100.30
7 purchase totals =	$1,067.81		$1,137.5265	$1,137.52	$1,137.55	$1,137.40