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	$228.68	9.710%	$250.8848	$250.88	$250.90	$250.90
Purchase #2	$234.32	3.281%	$242.008	$242.01	$242.00	$242.00
Purchase #3	$166.67	7.315%	$178.8619	$178.86	$178.85	$178.90
Purchase #4	$6.71	5.765%	$7.0968	$7.10	$7.10	$7.10
Purchase #5	$46.31	13.257%	$52.4493	$52.45	$52.45	$52.40
Purchase #6	$144.71	13.458%	$164.1851	$164.19	$164.20	$164.20
Purchase #7	$190.88	4.589%	$199.6395	$199.64	$199.65	$199.60
7 purchase totals =	$1,018.28		$1,095.1254	$1,095.13	$1,095.15	$1,095.10