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	$39.94	6.280%	$42.4482	$42.45	$42.45	$42.40
Purchase #2	$132.59	8.711%	$144.1399	$144.14	$144.15	$144.10
Purchase #3	$248.73	8.693%	$270.3521	$270.35	$270.35	$270.40
Purchase #4	$51.89	7.634%	$55.8513	$55.85	$55.85	$55.90
Purchase #5	$110.44	8.223%	$119.5215	$119.52	$119.50	$119.50
Purchase #6	$159.63	7.133%	$171.0164	$171.02	$171.00	$171.00
Purchase #7	$243.76	6.552%	$259.7312	$259.73	$259.75	$259.70
7 purchase totals =	$986.98		$1,063.0606	$1,063.06	$1,063.05	$1,063.00