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	$45.96	4.102%	$47.8453	$47.85	$47.85	$47.80
Purchase #2	$40.55	8.278%	$43.9067	$43.91	$43.90	$43.90
Purchase #3	$219.37	4.821%	$229.9458	$229.95	$229.95	$229.90
Purchase #4	$195.79	6.269%	$208.0641	$208.06	$208.05	$208.10
Purchase #5	$221.92	9.315%	$242.5918	$242.59	$242.60	$242.60
Purchase #6	$108.67	3.560%	$112.5387	$112.54	$112.55	$112.50
Purchase #7	$191.61	3.506%	$198.3278	$198.33	$198.35	$198.30
7 purchase totals =	$1,023.87		$1,083.2202	$1,083.23	$1,083.25	$1,083.10