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	$46.29	8.302%	$50.133	$50.13	$50.15	$50.10
Purchase #2	$73.64	8.724%	$80.0644	$80.06	$80.05	$80.10
Purchase #3	$102.97	6.479%	$109.6414	$109.64	$109.65	$109.60
Purchase #4	$98.80	10.500%	$109.174	$109.17	$109.15	$109.20
Purchase #5	$99.36	9.832%	$109.1291	$109.13	$109.15	$109.10
Purchase #6	$173.94	11.738%	$194.3571	$194.36	$194.35	$194.40
Purchase #7	$40.89	4.105%	$42.5685	$42.57	$42.55	$42.60
7 purchase totals =	$635.89		$695.0675	$695.06	$695.05	$695.10